Introduction

Migration is a complicated, improvised, and often unknown experience that depends on and reaffirms processes of social exclusion and inequality (^{Collyer, 2007}). Since the 1980s, economic insecurity in Central America, various forms of violence and social struggle in the postwar period have been the main reasons that have precipitated migration (^{Moodie, 2011}).

The migration patterns to and through Mexico are different (^{Suárez et al., 2017}). In recent decades the most frequent group of people going towards the United States were men looking for temporary work. Today women and children also migrate, however, with greater emphasis since 2011 rather than having as their goal to work in the United States, complete families of the Northern Triangle of Central America,¹ request asylum as the only way of protecting their lives. Some other immigrants want to reunite with their relatives who live in America (^{Varela Huerta & McLean, 2019}; ^{Hernández et al., 2019}). On the other hand, Mexico is no longer a protecting country for immigrants without legal documents (^{Soberanes Fernández, 2008}); it is a dangerous place where these vulnerable groups of people risk their freedom and lives.

Since 2010 the flows of families from Central American and unaccompanied children find their ways to move along the country traveling northbound (^{Albiac, 2019}; ^{Comisión Nacional de los Derechos Humanos [CNDH], 2018}; ^{Varela Huerta & McLean, 2019}). Staying in their countries has become a less viable option, even though Mexico is the third-largest country in Latin America, and the journey is long and challenging. These current massive movements towards Mexican territory reveal that they prefer to take the risk even though they are aware of the difficulties of the outmigration (^{Soberanes Fernández, 2008}; ^{Hernández et al., 2019}). Migration occurs despite knowing that they will end up facing an unfavorable and unhappy environment in the Mexican territory (^{Correa-Cabrera, 2014a}).

Taking the advantage of the needs of immigrants and seeking to obtain more economic resources, organized criminality found a method to get illegal money through them (^{Soberanes Fernández, 2008}). Cartels have even succeeded in corrupting Mexican authorities who allow the former to perpetrate such crimes or even collaborate in committing crimes against immigrants.

The paper explains the migration patterns of Central Americans, it then describes the impacts and effects that the Mexican drug war had on this vulnerable group of people, focusing on their kidnappings and enforced disappearances. The article correlates the steady inflow of immigrants through Mexican territory with their rate of entry into the United States along with the southwest border migrant apprehensions by the United States (US). It also spells out the missing immigrant records during the analyzed period and correlates them with the rising rates of violent crime carried out by drug cartels.

The central issue in the investigation of this article is whether or not the drug war in Mexico² was a factor that caused intense violence, which resulted in immigrants’ extortions, kidnappings and disappearances. The stages of the investigation involve 1) documentary research used to identify two separated phenomena: Central American immigration and the war against drug trafficking in Mexico. The reports under consideration included reports and briefs by the National Commission on Human Rights in Mexico, the Inter-American Commission on Human Rights, and materials provided by The Washington Office on Latin America. 2) It was also necessary to explore the levels of violence, which abruptly grew during the analysis period. In this part, using historical data and the instrumental method of demonstration, a statistical analysis of the information collected was carried out with the purpose of finding the interdependence relationships between the variables studied. 3) A study of the immigrant flows in Mexico, the rate of Central Americans entering the American territory, and the number of Central American apprehensions and deportations. These events were graphically illustrated using the information provided by the National Institute of Migration in Mexico (INM, by its acronym in Spanish), the US government, the US Border Patrol, and other organizations.

This manuscript shows that during the war against drug trafficking, the number of immigrant kidnappings, disappearances, and murders at the hands of criminal organizations multiplied manifestly. This paper explored the migration patterns in Mexico from 2006 to 2012 when the “narco war” was underway and found that, coincidentally during this period, the number of detentions and deportation of undocumented immigrants decreased (^{Correa-Cabrera, 2014}a). The arrests and deportations of immigrants after the war on drugs increased again in the 2012-2018 administration. After contrasting these numbers and based on the events and information referred here and the way they intertwine, it can be inferred that criminal violence against immigrants was a product of the Mexican war against drugs. It was finally found that the drug war in Mexico and northward migration were not separate phenomena; immigrants became the collateral damage of the ongoing battle.

Unsafety along their journey

Citizens of the North Triangle countries continue to march across Mexico to the US border Mexico’s proximity (^{Menjivar & Abrego, 2012}; ^{Albiac, 2019}). The reasons why Central Americans migrate have changed, in the past, were mainly the men who traveled to the United States to work and send remittances to their home-countries; this situation has changed and for two decades the reasons or push factors were different. The North Triangle of Central America is considered one of the most dangerous regions in the continent and in the world. In this scenario, the factors that motivate the migration of complete families are not only poverty but also insecurity, persecution, death threats, civil wars, and criminal violence (^{Albiac, 2019}, p. 11; ^{Leutert, 2018}; ^{CNDH, 2018}; ^{Hernández Hernández, 2019}).

Paradoxically, thousands of people in search of safety find an unsafe and hazardous way that is predictable but still preferable for them (^{Correa-Cabrera, 2014}a; ^{Medina, 2014}). Serious accidents are common along migration routes: intense heat, as well as falls and accidents while riding and jumping on and off moving trains, are everyday happenings (^{Barrón Cruz, 2013}).

Additionally, because of the increasing controls on highways, Central Americans must take isolated alternative routes and walk along quiet and long roads (^{Albiac, 2019}). They also have to take clandestine means of transportation such as freight trains and railroad cars where tens of immigrants stay crowded and hidden (^{Barrón Cruz, 2013}; ^{Shoichet, 2012}). Such conditions result in a hazardous journey. Smugglers take advantage of the immigrants’ intention to arrive at the US-Mexico border (^{Soberanes Fernández, 2008}). Smugglers have planned new strategies and are equipped and organized to move immigrants exposing Central Americans to shootings and kidnappings in the United States (^{Palacios Izcara, 2017}; ^{Tobar, 2009}) and Mexico. Smugglers know that Central Americans have relatives in the United States who can help with transportation costs for travel to the north and provide transportation without security or humane conditions.

Immigrants also encounter people who link them to more isolated and dangerous routes that overlap those used by organized criminals transporting drugs north. Because criminals perceive undocumented immigrants as a source of economic resources, their journey is valuable in illegal economic contexts (^{Coutin, 2005}; ^{Menjívar & Abrego, 2012}). In this scenario, undocumented foreigners are robbed, extorted, and abducted, or even killed by criminals, when their purposes are not achieved.

They are also objects of sexual exploitation, labour, human trafficking or even organ trafficking, in other words, their lives are exchanged for cash. As ^{Harvey (2005}) reported, “in the value of migrant life exchange, the bodies, work and life of immigrants are transformed into useful objects of exchange and exploitation”. Since criminal organizations regard immigrants as commodities (^{Menjívar & Bejarano, 2004}), their operations against them such as mass kidnappings are the result of well-organized networks where multiple actors, including authorities, participate.

The unauthorized status of immigrants contributes to their vulnerability, commodification as well as violence against them (^{CNDH, 2018}; ^{Coutin, 2005}; ^{Vogt, 2013}). Trying to evade deportation, they prefer to be unnoticed and avoid denouncing abuses and crime (^{Menjívar & Bejarano, 2004}).

This scenario is aggravated by cases of corruption of the US Border Patrol employees. Although empirical investigations of border corruption does not exist, there is serious research showing the American Border Patrol working in the South border is engaged in corruption practices. ^{Shirk (2011}) has mentioned that the penetration of US institutions by Mexican organized crime presents a serious problem along the border. According to ^{Flores (2017}), an investigation by The Center for Investigative Reporting registered 153 cases of corruption by the US Border Patrol (USBP) between the years of 2000 and 2013, a majority of which occurred in Texas. Among their activities they allow people to be smuggled into the country and provide information to cartels.

In addition to that, ^{Jancsics (2021}) cites a report on employee corruption and misconduct within the US Customs and Border Protection (CBP) published by the Government Accountability Office. It set out some insights into 144 cases, arrests of and allegations against CBP employees for corruption or misconduct between 2005 and 2012. Specifically, officials advised the smugglers which route they should take in order to avoid interdiction by USBP or provided information about the locations of sensors. On a relatively few occasions, Border Patrol agents actively participated in corruption by helping load vehicles with drugs or smuggling the drugs in their own car.

Impacts of the war against drug cartels

In 2006, at the beginning of his term, Mexican President Felipe Calderón declared war between the government and the drug cartels. One of the first operatives launched by the president was known as “Operativo Conjunto Michoacán” (^{Maldonado, 2012}). He deployed 6 500 soldiers and police officers─in specific areas of the State of Michoacan─with the purpose of searching and detaining people linked with drug trafficking and intercepting shipments of drugs. In 2007 President Felipe Calderon set up other army officers and heavily armed police officers in the northern states of Baja California and Chihuahua, as part of his war against drugs (^{Flannery, 2013}). Two years later, Mexico signed an agreement to tackle organized crime and implemented a plan against drug trafficking and kidnapping (^{Ortega Ávila, 2008}; ^{Leutert, 2018}; ^{Maldonado, 2012}).

Regardless of the capture of some members of a drug cartel and the seizure of shipments of cannabis, cocaine, and methamphetamines between years 2007 and 2011, the drug war produced several consequences such as the presence of 45 000 Army troops in the streets (^{Rodríguez Sánchez Lara & Aguilar Romero, 2020}). It also brought about thousands of murders from the battles between authorities and drug traffickers (^{Maldonado, 2012}), the seizure of several communities by drug cartels and the increase of human right violations by the Army, among some other impacts. Nevertheless, the flow of illicit drugs did not decrease.

The Mexican President´s strategy against drug dealers was militarization (^{Rosen & Zepeda Martínez, 2015}). With this plan, he intended to dismantle the illicit criminal networks that traffic drugs into the United States. He executed a policy of containment and weakening of drug trafficking organizations with the participation of federal, state, and local elements of the police force and the army. Felipe Calderon spent $46.6 billion in the fight against drug cartels (^{Seelke & Finklea, 2017}) and according to ^{Pereyra (2012}) the war resulted in 50 000 deaths. Some other sources refer that there were more than 70 000 homicides during that battle (^{Rosen & Zepeda Martínez, 2015}). In the previous administration, the federal government affirmed that there were 70 000 deaths as a result of the drug war. There is a record of 18 murders per day between 2008 and 2009 (^{Shirk, 2010}).

This course of action led to unprecedented levels of violence. Figure 1 shows that the number of drug-related murders increased sharply after 2006. According to ^{Robles, Calderón and Magaloni (2013}), the number of murders between 2006 and 2010 reached 80 976.

Figure 1 Levels of violence in Mexico after 2006 

It is interesting to note that in 2009 there were six times more deaths from drug trafficking crimes than in 2005. The number of deaths caused by organized crime and drug trafficking increased from 1 573 in 2005, 2 221 in 2006, 2 673 in 2007, 5 630 in 2008 and 7 724 in 2009 (^{Gutiérrez et al., 2010}; ^{Escalante Gonzalbo, 2011}).

In order to present an overview of the situation of violence in Mexico after the proclamation of the narco-war, it is necessary to review the incidence of homicide before Calderon took office, that is, before 2006.

From 1992 to 2007 there was a downward trend in the homicide rate, producing a progressive decrease of 50% since the beginning of the administration of Salinas until Felipe Calderon’s first year. Figure 2 shows the high rates of violence in Mexico during Calderon’s presidency (2006-2012). They are mostly attributed to the drug war. According to ^{Marina (2013}), violence was a consequence of a crackdown against drug cartels.

Figure 2 Intentional Murders in Mexico  

Figure 3 shows the number of drug war related homicides during the analyzed period. The information was reported by the National Institute of Statistics and Geography (Inegi), National Public Security System (SNSP, by its acronym in Spanish), and Grupo Reforma.

Figure 3 Homicides related to organized crime and drug trafficking 

It should be mentioned that the measurement of violent events and murders related to the war on drugs was obtained primarily from data provided by the government, such as Inegi and SNSP however, the organized crime and drug trafficking murder rates were also compared to the numbers pointed out by other private institutions such as Centro de Investigación y Docencia Económicas (CIDE). CIDE received, anonymously, three databases, which recorded violent events that took place in the context of the war on drugs during the government of Felipe Calderón, specifically, between December 2006 and November 2011 (^{Atuesta et al., 2016}). CIDE designed a system of validation and codification of the information contained in the databases, validated the information rigorously and published the database. The events recorded by CIDE were aggressions, confrontations and murders³. The numbers published by CIDE were consistent to the ones mentioned in Figure 3.

It is convenient at this point to carry out a formal data analysis using Statistical Package for the Social Sciences⁴ (SPSS). This method produced the following results:

The correlations measure the relationship between two variables: homicides related to organized crime and drug trafficking. In this method, if the bilateral significance is equal to .000, the existence of the analyzed phenomenon is very high. As it is shown in Table 1, according to the analysis, the information reported by Inegi, SNSP and the one published by Grupo Reforma are consistent with each other. The information provided to the software is constant or showed the same behavior in 95% of cases. Specifically, the three sources coincide in an increase in drug trafficking-related violence during this period.⁵

Subsequently, the Pearson's coefficient was used to run correlations and significance in this case. This coefficient is frequently used to measure the association between the variables of interest, as it is based on the method of covariance. The Pearson correlation measures the statistical relationship and finds a linear relationship between two variables. In this particular case, the result (.982) is an indication of certainty of the phenomenon under study.⁶

Therefore, using historical data and the instrumental method of demonstration, when the number of drug related homicides is growing, it is reflected in the number of homicides in general, that is to say, they are part of the first phenomenon. With 98 per cent certainty, drug-related violence increased during this period.

This corroborates ^{Durán-Martínez’s (2015}) assertion that criminals prefer less visibility if they receive State protection. A contrario sensu, if they have less State protection and a war is declared against them, the result is greater drug-related violence.

Accordingly, during the drug war, some criminal organizations became powerful and were consolidated. Because of the federal intervention, drug cartels intensified the mass killings and attacks on police officers, soldiers, security officials, and civilians at the same time they blocked access to some Mexican communities (^{Pereyra, 2012}). In this produced fight for power, the levels of violence increased as it was the means of confronting the rivals and survive the threatening war (^{Pereyra, 2012}). Unfortunately, the rising mortality rate and the fact that people vanished without a trace were not only drug traffic-related, these occurrences were a direct result of the war against drugs.

Additionally, the number of murders and drug related murders recorded from 2007 to 2014 was provided to the software. The results were as follows:

According to the method used, Table 2 shows a very direct relationship between homicides and narco-executions, in such a way that they are associated phenomena. That means, if homicides increase by one percentage, narco-executions will increase by .95%.⁷

What effects did this confrontation have on immigrants going through Mexico?

Seeking to spread terror throughout society and dominate territories, some organized criminals exercised violence over civil society. While intending to obtain more money illegally, another of their objectives was extorting businesses. Drug traffickers also viewed undocumented immigrants as commodities from whom they could obtain large sums of money. In other words, many organized criminal groups diversified their products, using immigrants as goods or merchandise (^{Correa-Cabrera, 2014}b; ^{Da Silveira Moreira, 2015}).

The link between some organized crime groups and immigration is deep and complex (^{Selee, 2017}). The transitory status of immigrants through Mexico has created an intense activity for organized crime. Drug cartels have taken advantage of the major protection of Mexican authorities at the borders since they know it is difficult for an individual to cross these geographic boundaries. Given the vulnerability of undocumented immigrants, drug cartels are aware that Central Americans need to hire networks of smugglers (^{Soberanes Fernández, 2008}; ^{Leutert, 2018}, p. 19). As a consequence, the routes used by immigrants and smugglers have been overrun by these cartels (^{Departamento de Estudios Internacionales, 2014}).

It is worth mentioning that not all the drug cartels were involved in kidnapping and extorting money from migrants, in fact, analyzing the sources of information it was found that Zetas was the criminal group that mainly undertook other crimes such as extortion and kidnapping in addition to drug trafficking. Zetas are a criminal group characterized by their brutal use of violence. Their specialized knowledge of firearms and military tactics is due to the fact that the founders recruited deserters from the Mexican Armed Forces. Their first members were trained by the U.S. Army for counterinsurgency work at the School of the Americas. The recruitment process included 31 elite military personnel, later including others with less military training. Later, criminals were also included in the group. When the Zetas felt threatened by the drug war and other criminal groups, they sought economic resources in other ways. They mainly resorted to charging a “rental fee” to other criminal groups to let them operate. This strategy was used to conquer and control territories. The practice of charging a “rental fee” grew to include kidnapping and extortion. These criminal practices spread against the immigrants.

It is known that Zetas had a confrontation in Guatemala against the Sinaloa Cartel for access to South American cocaine and migrant routes. In Mexico, the states where immigrants were kidnapped and/or disappeared tended to be territories controlled by Zetas: Veracruz and Tabasco (2 944 and 2 378 immigrants kidnapped, respectively), Tamaulipas with 912, Coahuila with 17, San Luis Potosí with 15, and Nuevo León with 5. The 2009 Report by Comisión Nacional de los Derechos Humanos (CNDH) on the Kidnapping of Migrants, together with the behavior of the rate of missing persons─different from that of homicides─, and the statements of some migrants in San Fernando, Tamaulipas who survived the massacre, are important clues that cannot be ignored in this investigation.

These organized crime groups have studied how undocumented immigrants move, their routes, where they stop, and how they are transported. Drug cartels also impose charges on smugglers for letting immigrants go through certain routes; otherwise, they kidnap or even kill immigrants. Terrified by “los Zetas”, coyotes have accepted and agreed on the amounts to be paid to this cartel.

When undocumented immigrants travel on their own, cartels know they have to use these criminals’ “services” (^{Departamento de Estudios Internacionales, 2014}) and get the most out of this situation. Entering the specific business of human tracking, drug traffickers risk women, older people, and even children. Criminals leave immigrants in the middle of the dessert or transport them in freight trains (^{Barrón Cruz, 2013}), where these undocumented people travel in overcrowded conditions and suffocate (^{Rodríguez et al., 2011}).

Sometimes drug dealers kidnap immigrants knowing that they have relatives in the United States willing to pay the rescue for them (^{Leutert, 2018}). Seeing immigrants with cell phones makes criminals think that they have contact with family members in the US. According to Central American testimonies, “zetas” is one of the criminal groups taking that course of action (^{Barros, 2017}). To do this, criminals first acquire control over railroad routes, and then they intercept immigrants, keep them as hostages inside unknown places where these travelers are forced to call their families and ask for rescues between $4 000 and $5 000 dollars.

Organized criminal groups had to survive the war against them and while trying to find more people who can work for these criminal cells; undocumented immigrants are a good and easy prey (^{Shoichet, 2012}; ^{Suárez et al., 2017}). Central American immigrants are vulnerable people without documents to prove their identities most of the time, they do not know where to go when their rights are not respected and are not willing to press charges in government offices that can deport them.

In addition, these immigrants are good preys because they are seen as objects that can be sold and whose value can increase or decrease (^{Vogt, 2013}). In fact, human trafficking is a business that generates three thousand millions dollars. Undocumented women are associated with prostitution and are intimidated to work as such. Other women are victims of sexual tourism and suffer sexual or labor exploitation (^{Andrade-Rubio, 2016}). They are also forced to cook and clean their places. Both women and men are constrained to work for organized criminals because the last ones think Central American belonged to rebellious groups in their home countries (^{Casa del Migrante de Saltillo & Centro de Derechos Humanos Miguel Agustín Pro Juárez, A. C., 2011}; ^{Soberanes Fernández, 2008}). Even children and adolescents are convinced to work for them.

More specifically, cartel hitmen have made immigrants form part of these organizations making them collaborate in kidnappings and extortions. Police officers have found Central Americans that participate in criminal chains, either by coercion or because they do not have another option. Some undocumented immigrants had previously participated in criminal activities in their countries of origin. As a matter of fact, some immigrants have reported that some Central Americans help organized criminality groups in several activities, including kidnappings. They refer that Central Americans have reached medium level positions in the hierarchy of criminal bands and some are leaders in local groups.

This kind of crime exploits to their advantage the ineffective criminal justice system in Mexico with high levels of impunity and the unsuccessful criminal migration policy trying to reduce immigrants. Such measures have been put into effect by corrupt authorities such as police officers who have become a symbol of instability and impunity (^{Soberanes Fernández, 2008}).

Migrant kidnapping and enforced disappearances

Although most immigrant disappearances are never reported, evidence shows that kidnapping of undocumented immigrants is a generalized practice in Mexico (^{Correa-Cabrera, 2014a}; ^{Leutert, 2018}). According to CNDH, organized criminal groups abducted more than 9 758 immigrants in Mexico between September 2008 and February 2009 (^{CNDH, 2011}; ^{Da Silveira Moreira, 2015}).

There are no accurate statistics on the abductions and disappearances of immigrants. In fact, the lack of statistics is the effect of prosecutor authorities’ failure to open criminal cases for the disappearances of undocumented immigrants. On other occasions, victims or victims of relatives do not register a formal complaint, fearing that government authorities will deport them and some other times they do not follow up their cases because they are immigrants and leave the places where the crime was committed. Nevertheless, some victims have been able to describe how criminal organizations capture more than one hundred immigrants every time and how drug cartel members continue to perform their illegal conduct unpunished.

When relatives of a missing person decide to report the case to the Prosecutor’s Office, district attorneys reply they must wait for 72 hours after the disappearance to register a formal complaint. According to interviews with the victim’s relatives, obtained by Human Rights Watch, Federal prosecutors do not go to the places where relatives believe that the missing person is being held, and as a consequence, the discouraged relatives do not usually come back to file or follow up official complaints (^{Human Rights Watch, 2013}). The victims’ families have referred to Human Rights Watch that prosecutors give excuses for not taking their testimonies and for not opening their investigations.

The following are abduction cases known either by testimonies of people who escaped from the group of kidnapped immigrants or by the government investigators who found clandestine graves:

Amnesty International informed society that 36 immigrants were abducted by armed men and put in a freight truck in the state of Veracruz in November 2008. They were translated to Tamaulipas where a criminal band held more undocumented people who were forced to give their relatives’ telephone numbers.

Another representative case is one in which dozens of immigrants were held captive in Puebla in 2008 (^{Vogt, 2013}). The Committee of Relatives of Murdered and Disappeared Immigrants revealed that 294 Salvadorans were either murdered or disappeared by organized criminal groups in 2009 (^{Castro, 2008}). 72 immigrants were tortured and killed in San Fernando, Tamaulipas in 2010 (^{Hernández Hernández, 2019}) for not accepting to work for a drug cartel. Additionally, 49 bodies of immigrants, presumably from El Salvador, were found in Cadereyta, Nuevo León in 2012 (^{Shoichet, 2012}; ^{Varela Huerta, 2017}). One hundred thirty-two immigrants were kidnapped in La Sierrita, Sonora, and rescued in Sonora in February 2011. Some of them were from Guatemala, Honduras, and Nicaragua (^{Gutiérrez, 2011}).

The CNDH documented in February 2011, that 11 333 migrants had been kidnapped between April and September 2010. Seventy-six percent of these abductions, committed between April and September 2010, were against Central Americans. Sixty-four and 7/10 of a percentage of the captures took place in southeastern Mexico (^{Isacson & Meyer, 2012}).

Three immigrants, fleeing after being kidnapped, reported an event in the northern state of Coahuila Mexico. In November 2011, armed men stopped the train immigrants were riding, kidnapped 23 undocumented travelers from Central America, and forced them into pick-up trucks. The immigrants decided to file an official complaint before the Prosecutor’s Office; however, the government did not start an investigation on this case (^{Human Rights Watch, 2013}).

The kidnapping story increased during the war against drug cartels. Specifically, the cruel treatment towards immigrants increased in Mexico when strategies against organized crime were implemented under Felipe Calderon’s administration.

After these crimes, that only account for a small part of the problem, the United Nations Special Rapporteur´s Report on the Human Rights of Immigrants specified in March 2009 that organized criminal bands involved in drug trafficking and human trafficking were making a lucrative business out of immigrants and that federal, state and local authorities were participating with them. The places where more violence was inflicted were in the northern and southern borders of Mexico and in transit places for immigrants. The report also mentions that most of their victims were individuals from Guatemala, El Salvador, Honduras, and Nicaragua.

Some of the kidnapped immigrants have been victims of human trafficking, The Federal Institute of Defense Attorneys in Mexico reported several complaints on migrant disappearances. According to their testimonies, these undocumented foreigners were delivered to organized crime groups (^{Terra, 2011}). Figure 4 shows that this crime increased sharply from 2009 to 2013.

Figure 4 Human Trafficking in Mexico from 2009 to 2013 

The war on drugs and the disappearance of migrants in Mexican territory

This paper proposes that the cause of the missing migrants was the fight against drug cartels occurring in Mexico from 2006 to 2012. Why can we infer that? Five happenings evidence that.

1. Inflow of immigrants in transit through Mexican territory and deportation rates

First, the traditional inflow of immigrants entering the Mexican border did not decline during those years. In fact, every year, an average of 500 000 immigrants from Central America enters the southern border of Mexico. Even though the influx was steady during this period, government statistics reveal that not only immigrants traveling northbound but also the number of deportations fell off.

Figure 5 Volume of undocumented migrants from Central America (millions of people) 

As shown in Figure 5 and according to ^{Canales Cerón and Rojas Wiesner (2018}), irregular migration of Central American origin shows a sustained growth trend, from 1.35 million in 2006 to 1.6 million in 2014.

Figure 6 Estimate of the migration flow of Central Americans in irregular transit through Mexico 

Figure 6 shows that even when the entry of immigrants had already peaked in 2005, the Central Americans who were traveling inside the Mexican territory declined consistently. In other words, despite the regular number of immigrant entrances in the Mexican territory, the numbers show that the flow of undocumented Central American migrants in transit through Mexico decreased from 199 000 in 2007 to 157 000 individuals in 2008. While 131 000 immigrants were traveling in Mexico in 2009, the number decreased to 127 000 in 2010 and to 126 000 in 2012.

Besides that, the number of deportations by Mexican and American authorities decreased dramatically during the analyzed period. By the time the drug war was declared, there were already firm control immigration policies and programs such as Operación Centinela in 2003 and Plan Sur, which were implemented and used detention to reduce migration into the United States. Notwithstanding it, the reduction in migrant deportations during the drug war became evident.

Deportations went down after 2006, even after the US Patriot Act of 2001 authorized a tripling of the number of Border Patrol personnel, Customs personnel, and immigration inspectors along the Northern Border (^{Jenks, 2001}), which inherently meant more apprehensions. In 2002, Mexico becomes part of a program called “Fronteras inteligentes” (Smart borders) which includes security, criminal justice system, and strict immigration policies. Under this program, better technology would be used and more public servants would be hired to protect the borders (^{Correa-Cabrera, 2014}a; ^{Emmerich, 2003}).

This manuscript argues that although Mexico received a steady stream of undocumented foreigners, the data disclose that the number of immigrants caught by the U.S. Border Patrol in the Southwest Sector and by the National Institution of Immigration in Mexico markedly declined from 2006 to 2012. Even with major border control programs in the South of the United States, the USBP could not apprehend and deport Central Americans because they did not arrive at the border, they were intercepted by organized criminality. According to this, a study by The Washington Office on Latin America (WOLA) and El Colegio de la Frontera Norte (El Colef) sets out that “U.S. authorities have registered a remarkable 61 percent drop in apprehension of migrants at the southwest border between 2006 and 2011”.

The following chart shows that apprehension and deportations have dropped to early 1970s levels.

Figure 7 Southwest border migrant apprehension by the US 

As shown in Figure 7 the Report by Instituto Nacional de Migración (INM) specified that the number of Central Americans detained by Mexican INM slowed down continuously from 2006 to 2011. This study found that more than a hundred thousand immigrants used to be apprehended in Mexico every year before the drug war. For instance, 133 975 immigrants were apprehended in 1999 and 170 447 in 2000. However, the number of Central Americans deported from the Mexican territory declined to 64 061 in 2009, 63 567 in 2010, 59 386 in 2011 and 68 367 in 2012 (^{Secretaría de Gobernación [Segob], 2013a}).

In reality, people seek to migrate regardless of the set of enforcement policies intended to apprehend, punish, incarcerate, and criminalize unauthorized migrants at the border (^{Knox, 2017}; ^{Slack et al., 2015}). In other words, such measures do not discourage immigrants to experience mobility to improve their lives. Certainly, the complicated situation in Central America did not change during those years and thousands of Guatemalans, Hondurans, and Salvadorans continued to flee insecurity in their home countries (^{Secretaría de Gobernación [Segob] & Instituto Nacional de Migración [INM], 2012}).

Unsurprisingly and according to this paper’s thesis, the number of Central American migrants who were deported to their home countries by the Mexican authorities has maintained a constant growth since 2012. For instance, more than 70 000 Central Americans deported in 2013, more than 100 000 in 2014, and 150 000 in 2015 (^{Segob, 2013b}).

2. Lower rate of Central Americans entering the United States

Remarkably, during the war against drug cartels the number of immigrants who managed to enter the United States declined. The Northern Border International Migration Survey (Encuesta Sobre Migración en la Frontera Norte de México, Emif Norte) by El Colef found that the inflow of migrants going from Mexico to the United States dropped in 2008. As a consequence, the number of migrants entering the United States fell from 841 000 in 2007 to 492 000 in 2010. At first glance, logically speaking, a consistent increase in the number of immigrants coming to Mexico every year at the same time that fewer apprehension and deportations occurred, entail that a greater number of unauthorized immigrants entered the United States; however, it did not happen that way, there was a lower rate of immigrants arriving in the United States during that period.

With migration flows increasing until 2006 and fewer deportations occurring, the deterrence strategy had failed. However, the decreasing number of flows to the US has to do with the number of murders and kidnappings committed by Mexican drug cartels. In other words, the reason for that fall is not only the deterrence strategy; it is the fact that drug cartels became predators of immigrants without legal documents.

Some facts suggest that the inflow of immigrants arriving in the United States started to change in 2007. For instance, Nuevo Laredo is one of the places undocumented immigrants from Central Americans choose while crossing the US-Mexico border since it is not as difficult as the desert areas in Arizona, California, or Nuevo Mexico. According to a shelter known as The Nazareth House, located in Nuevo Laredo, USA, approximately 10 000 immigrants per year used to stop in the house on their way north. This number significantly changed, especially from 2009 to 2011, when the number of people arriving in the shelters dropped below 6 000 in 2010. Half of those were undocumented migrants who had been deported, in other words, they were not going northbound. Additionally, there were more Mexicans than Hondurans in the shelter in 2009, and in 2010, most of the people taking refuge in the shelter were Mexican (^{Baggio, 2011}).

3. War against drug cartels and violent climate for immigrants

Central American citizens have been pushed to flee from their countries because they want to abandon violence and crime; however, they fall into the hands of criminals and people who steal whatever they have. Families of undocumented immigrants reported having faced disappearances, death threats, and some of their children have been recruited by criminal groups. In other words, they are victims of intense violence (^{Vogt, 2013}).

Drug cartel activities are inherently violent because of the limited crossing points available to conduct illegal activities. Nevertheless, the war against drug traffickers resulted in some unexpected consequences: exacerbation of violence, kidnappings, and murders against civil society and vulnerable groups (^{Guerrero, 2013}). Following the announcement of the war, criminal organizations resorted to violence as the primary way they could defend themselves and control more territories (^{Pereyra, 2012}). The value of controlling those territories is stratospheric, and creates incentives to fight violently to get that control. Violence is a means of subsistence for criminal organizations and a revenge instrument against authorities, opposing cartels, and even against the civil society. It is also a resource to diversify an illegal business.

The type of violence applied to individuals by organized criminality is characterized by the intention to intimidate those considered rivals. In that sense, dismember, hung, and decapitated bodies are daily images of violence associated with organized crime in Mexico (^{Andrade-Rubio, 2016}; ^{Izcara-Palacios, 2012}). Drug cartels exert violence to compete for control of territories and to attack and intimidate law enforcement and society in general.

During the drug war, drug trafficking organizations strengthened, fought for power, and became rivals wanting to expand business territories (^{Pereyra, 2012}). ^{Maldonado (2012}) has affirmed that both the anti-drug policies and corruption, led to the emergence of criminal organizations.

The number of Mexican opiate trafficking criminal organizations increased from 6 cartels in 2006 to 9 cartels in 2010 (^{Barreda Vidal, 2014}) and 16 cartels in 2012 (^{Rosen, 2015}). In this scenario, drug cartels fought among themselves to have more presence in the country and to control more territory. With the purpose of obtaining more money, they undertook various illegal activities (^{Guerrero, 2010}), such as selling weapons, practicing extortions, trafficking humans, trafficking human organs (^{Leutert, 2018}); in other words, selling and transporting drugs would not be their only business anymore. During these years, it was found that some drug cartels reorganized in new criminal organizations.

To survive the war, drug cartels invested large sums of money in personnel, equipment, and weapons (^{Ravelo, 2010}). Sinaloa, del Golfo, and los Zetas Cartels started to have increased international mobility in their unlawful activities. They recruited people who became hit-men and who were trained in paramilitary techniques, diversified the type of product they smuggle, got access to weapons, and got more non-legal funding sources. As part of their survival strategy, they hired gangs and young vulnerable people to face the human losses caused by the drug war. In other words, organized criminals became undocumented immigrant hunters. The other drug cartels having more control in the center, south, east, and south of the country undertook illegal businesses less profitable than large-scale drug trafficking but more risky and violent, such as kidnapping, extortion, human trafficking as well as vehicle and back thefts (^{Pereyra, 2012}).

What is the relation between the drug war and violence against undocumented immigrants? Firstly, immigrants are vulnerable people who become even more defenseless due to violence, which is a central mechanism allowing profits to be derived from. The type of violence immigrants suffer changed; whereas in the past migrants encountered thieves who stole their money and disappeared from their routes, nowadays, immigrants know there are solid links between organized crime and police (^{Vogt, 2013}).

Viewed as commodities (^{Vogt, 2013}), undocumented immigrants have become targets for gang-related crime. Seeking to continue in the black markets and illegal business, drug cartels operating in Mexico use immigrants as coerced labor and exploit them as they move through the country (^{Andrade-Rubio, 2016}). In the last few years, regions with flows of immigrants have been controlled by organized criminality and some corrupted public servants working for security or the prosecutor’s offices. Unfortunately, in México one of the factors that favor violence is the weak institutional capacity of local and state governments (^{Armijo Canto, 2011}).

To illustrate this situation, the most common crimes against immigrants in strategic states, such as Chiapas, Oaxaca, Tabasco, and Sonora are assault, theft, and robbery with violence. In other parts of the country, the crime of trafficking human prevails. People pressed charges for human trafficking 260 times. (^{Suárez et al., 2017}). According to the data obtained, the most common local jurisdiction crime against them is robbery (^{Shoichet, 2012}; ^{Suárez et al., 2017}, p. 10). While human trafficking is the most frequent federal jurisdiction crime (^{Suárez et al., 2017}). Sexual violence against immigrants is also perpetrated. According to non-profit organizations, six out of ten women are abducted in their journey to the United States (^{Castro, 2008}). In this scenario, where drug cartels try to be more powerful, criminal organizations endanger undocumented individuals going through Mexico.

Although the war on drug trafficking aimed at bringing down the drug lords; it had destructive effects on undocumented immigrants. The Mexican drug war created a spiral of violence. Besides, organized crime rose sharply against northern-bound migrants, who had little or no protection from the government.

4. Missing immigrant records

Criminals see undocumented migrants as a source of economic resources that need to dominate the territories and survive the war against organized crime. They carry the heavy weapons and sophisticated artillery that is used to kidnap and to extort immigrants without legal documents. There are thousands of victims of kidnappings committed against undocumented Central Americans in Mexican migrant routes (^{Leutert, 2018}, p. 30). In general terms, official sources report only a small part of this type of criminality, concealing the violence against this vulnerable group of people. For instance, the mentioned events in San Fernando were portrayed as unusual, abnormal, strange, and isolated, nevertheless; it is only one of the daily unfortunate disappearance events happening to undocumented immigrants.

When we studied this period we found that by the time the number of drug cartels grew, the number of undocumented immigrant kidnappings and murders rose significantly. We already mentioned that during the war against drug traffickers the number of Mexican cartels increased from 6 to 16 (^{Seelke & Finklea, 2017}). Correspondingly, by the end of 2009, organized criminal groups kidnapped almost ten thousand immigrants in Mexico. One year later, the CNDH estimated that the number of abductions amounted to 11 000 (^{CNDH, 2011}). This unprecedented number of kidnappings was also recorded by the two Human Rights Commission’s Briefs: “Informes especiales sobre secuestro en contra de migrantes” de la Comisión Nacional de los Derechos Humanos (“Special report on kidnappings against migrants” of the Human Rights National Commission) where the Commission specifies that every six months 10 000 people were victims of this crime. The Brief pointed out that the number and violence of abductions had gone up to 20 000 each year (^{CNDH, 2009}).

Of all known cases of migrant abductions, CNDH reported that 55% of the victims were kidnapped in the south of the country, 11.8% in the north; 1.2% at the center, while it was not possible to specify where 32% of the victims were abducted. ^{Leutert (2018}) refers to the Central American Migrant Risk Database, which identified Chiapas, Veracruz, Coahuila, and Tamaulipas─area constituting an important migrant corridor─as the places with the most migrant homicides and disappearances.

With the police criminal investigation and testimonies of the victims who could escape from hostage houses, it was possible to elaborate a map of high-risk areas for the commission of abductions on the migrant route.

Regardless of the diverse federal and local record-keeping systems, the 2012 Brief presented to the Interamerican Commission of Human Rights named “Report situation of missing migrants and unidentified remains in Mexico” (Informe situación de las personas migrantes no localizadas y restos no identificados en México) presents an estimate of 70 000 migrant disappearances in the period of 2007 and 2010.

5. The actions taken by the government, government institutions, and civil society evidence the magnitude of the problem

Because of all those events and victims’ demands, the National Commission on Human Rights (CNDH, by its acronym in Spanish) signed the Framework Partnership Agreement to collaborate in preventing and fighting migrant kidnappings on August 31st, 2010. According to this Agreement, the Commission would collaborate with the Secretary of Government, the General District Attorney, the Secretary of Public Security, and the National Institute of Migration to reduce the crimes towards immigrants (^{CNDH, 2011}).

Between 2009 and 2010, several civil organizations prepared the following reports: “Kidnappings of Central American migrants in transit of Mexico”, “Report situation of missing migrants and unidentified remains in Mexico”, “Invisible victims: migrants on the move in Mexico” and “Sixth report on the situation of the Human Rights of Migrants transiting Mexico”. The first two reports were addressed to the inter-American Commission on Human Rights.

In 2010, more than ten civil society organizations asked the inter-American Commission on Human Rights for a public hearing and presented the systematic and widespread abduction to the detriment of migrants in Mexico, committed by organized crime.

The seriousness of the situation and the ineffectiveness of Mexican search methods have resulted in the arrival of the immigrants’ relatives where mothers, sisters, and cousins from Honduras, El Salvador, Guatemala, and Nicaragua come to Mexico and demand to know the whereabouts of their family members. They have not obtained the truth; however, one of the actions of the Mexican government was to set up the first Prosecutor's Office Specialized in Crimes Committed against migrants in the southern state of Chiapas. Subsequently, other specialized offices were created in other states.

Conclusions

The phenomenon of immigration in Mexico changed dramatically just after the war against drug cartels was declared in Mexico in 2006. The intense violent atmosphere that emerged during the six following years brought about collateral damages for the vulnerable group of immigrants without legal documents traveling northward. In order to survive the drug war and gain more control, trafficking organizations learned to make a profit out of thousands of unauthorized foreigners. They also took advantage of easily corrupted authorities and the weakness of government institutions.

During the analyzed period, the repressive climate created by the government reached irregular immigrants who endured tragic episodes such as ongoing threats, human trafficking, kidnapping, exploitation, slavery, and murders committed by organized criminality. Some drug cartels expanded their domains, diversified their illegal activities, created sophisticated methods, and obtained the weapons to extort and or exploit Central Americans.

This article illustrated and showed concise evidence demonstrating that criminal organizations put immigrants in great danger during the drug war. First, the migration rates in the Mexican territory remained largely stable, however, the number of immigrants entering the United States declined those years. Second, even though there were strict control border policies, the number of immigrant apprehension and deportations fell off. Third, the fight against drug trafficking prompted higher levels of violence and the existence of more drug cartels that saw immigrants traveling as merchandise. The commodification of undocumented Central American immigrants resulted in an unprecedented number of extortions and abductions perpetrated by the spiral or organized crime.

For this study, an exhaustive search for information on migrant disappearances in Mexico was conducted. The information presented is what is available, recognizing that the number of reports is very low and that many missing migrant bodies have disappeared without being registered. Unfortunately, the government does not show the real numbers of migrant disappearances, even thought, mothers of abducted immigrants reported before Mexican authorities and human rights organizations the cases of their missing relatives. In addition to their demands, immigrants who escaped their own kidnappings gave testimonies about how they were captured by organized criminals. The violent phenomenon against undocumented immigrants increased during the Mexican drug war, as it can be inferred in this study.

Paradoxically, with the fight against organized crime, the levels of violence rose sharply in Mexico.

Drug cartels strengthened intimidating society and committing crimes. It does not mean that the national security approach along Mexico’s southern border did not have as a consequence an important number of apprehension and deportations for irregular immigrants, such was the case. However, what violated the integrity and freedom of immigrants traveling through the country during the drug war period was the increased levels of violence, which coincided with elevated rates of abductions and murders. The statistical information showing the interdependency relationship between the drug-related crimes and the Mexican battle against drugs was carried out taking into account drug trafficking murders, information that is provided by several reliable sources.

In this scenario, the role of non-government organizations and civil society was significant, as they not only provided society with more realistic information on crimes suffered by undocumented immigrants in their perilous immigrant trails but also assisted immigrant relatives conducting the criminal investigation denied by the government.