Thousands have died in a wave of drug-related violence in Mexico [Reuters]

As part of "Mexico in the Crossfire", Al Jazeera's special coverage on the war between the government and drug cartels, we speak to one of the gangs' so-called "foot soldiers" about why he joined the organisation, the brutal nature of his work and why corruption is fanning the flames of violence.

With his warm grin and brown eyes, "El Cholito" does not appear to be a violent man.

But his face abruptly changes and his stare becomes harder when he describes how he was part of drug cartel hit squad that tortured rival traffickers for two days before shooting them in the head.

"We were just doing our job. I don't regret it. It is pure business," the 26-year-old says, showing no emotion as he reveals his role in Mexico's relentless drug war during an interview in a house in the southern state of Oaxaca.

In depth

The testimonies of Cholito and other street-level cartel members like him have been providing important insight into the way cartels operate and how they have managed to overwhelm the Mexican army in many parts of the country.

Cartel recruitment

The cartel finds fertile recruiting ground among Mexico's young poor [EPA]

Backed by the US, Felipe Calderon, the Mexican president, is leading a nationwide crackdown against the crime families. He is sending 50,000 soldiers, federal police and special agents to arrest them in urban slums and marijuana-growing mountains throughout the country.

But the cartels have responded with violence on an unprecedented scale, committing 7,000 drug-related killings - including 700 police and soldiers since January 2008.
 
The stories of Cholito and others reveal some of the cartel tactics that have allowed them to sustain such a high level of killing while under intense attack.

A native of a small working class town in Oaxaca, Mexico's poorest state, Cholito worked as builder before he was recruited into a crime family that set up operations around his hometown two years ago.

He was initially paid just $800 a month, but this soon doubled to $1,600 as he rose through the ranks.

"It may not seem [like] a lot of money to Americans or Europeans, but in the neighbourhood where I grew up, my wage makes me richer than most people," he said.

One of the key strengths of the cartels is that they are able to recruit foot soldiers from among the millions of poor young Mexicans who have little loyalty to their government.

Making an estimated $30bn a year selling marijuana, cocaine, crystal methamphetamine and heroin to US users, the cartels are able to hire tens of thousands of people to work for them, doing everything from counting money to watching roads. 

Hard to infiltrate

This endless stream of new foot soldiers, often with no criminal records, makes it difficult for the Mexican authorities to monitor and hunt down their enemy.

Cholito said his first job was simply to watch a key highway running through his state, reporting the movements of police, soldiers and anyone else who seemed suspicious.

The cartel wanted to protect their merchandise, in Oaxaca, which is also one of Mexico's largest marijuana-producing states and a key transit point for drugs heading north.

A year into his work, Cholito began accompanying his bosses to collect payments from local dealers and growers.

On one occasion, they abducted two dealers who refused to pay what they owed, beating and stabbing them for two days before they shot them to death and dumped their bodies.

Cholito says he only knows the men he works with by aliases, such as "El Cholo," "El Indio" and "El Gringo."

This use of code names and cells of operatives makes the cartels extremely hard to penetrate, with arrested foot soldiers having no knowledge of the real names or origins of those around them.

Military tactics

The same tactic is used across the warring cartels, as confirmed in a statement by Marco Vinicio Cobo, alias the "Nut Job" – a 30-year-old man accused of being involved in the decapitation of a soldier last April.

Cobo was accused of being involved in the murder of a security official

Cobo confesses that he worked for the Gulf Cartel and their ruthless gang of enforcers known as "Las Zetas", who are based close to the US border.

Cobo revealed that the Zetas use a vertical, military-style chain of command to control thousands of men.

"I began as an H — the code they use for Hawk," he says of his rank. "After a time, I became a Central. I gave information to all the local H's in the community."
 
Cobo had 13 Hawks under his command and reported in turn to a second commander.

The Zeta ranking system is based on the Mexican military hierarchy.

This is hardly surprising as the organisation was founded by soldiers from the army's special forces who defected to the drug lords in the late 1990s.

'Hit squads'

The scale and trail of dead bodies is overwhelming Mexican authorities [AFP]

"They kidnapped people who had committed what they said was a crime," he said.

"Many were people who worked as drug traffickers."

In March, they spotted a military intelligence officer who was delving too deeply into their operation.

A Zeta hit squad is believed to have kidnapped, murdered and decapitated him, dumping his body on a road.

Following the killing, soldiers arrested Cobo and 13 others, and seized semi-automatic rifles and radio equipment.

Corruption concerns

He said his boss, known by the alias "Franco", had a book with names of dozens of police officials on Zeta's payroll, including officers from many nearby towns and federal agents stationed there.

The corrupt police were also given aliases, including "Papa" and "Brother".
 
Like Cholito, Cobo came from a modest background, working as a crime reporter for a small-town newspaper before he left to join the Zetas, who paid him about $800 per month when he joined the gang - a far cry from the billionaire kingpins with their mansions and fleets of planes.

But many foot soldiers feel that by joining the cartels they may one day aspire to such riches.

Cholito said he has no desire to change his lifestyle, even though it could lead to death or jail.

"I could never go back to making $10 a day," Cholito says smiling broadly.

"At least in the cartel, I get paid and I have some opportunity to rise up. In other jobs, I will always be at the bottom."