Nearly four years into its battle with the drug cartels, the Mexican army has learned some hard lessons.
Its role has been redefined. It is now a virtual domestic police force in Mexico's drugs conflict, in which an estimated 30,000 people have died since late 2006.
That new role has brought increased funding, but also a higher profile and with it, closer scrutiny.
And that in turn has not always shown the army in a good light.
In December 2006, Felipe Calderon took office as president and commander-in-chief of the armed forces.
A few days later, he called upon the forces to fight the drug cartels, invoking their constitutional role of maintaining the integrity and security of the state.
It was a controversial decision. But four years on, young recruits insist they see the protection of their homeland's security as one of their key missions.
Carlos Vargas joined the army less than two months ago and is completing his initial training at an army barracks outside Mexico City.
"I am proud of defending my country from people who want to hurt it," he says.
There are now 45,000 soldiers patrolling the streets of cities like Ciudad Juarez, on the border with the US.
But accusations of human rights abuses by members of the military are increasing, and many in Mexico think the army is paying too high a price for its new role.
Unlike in most Latin American countries, the Mexican army was never involved in a coup or faced accusations of massive human rights abuses.
The army, currently some 250,000 strong, still ranks as one of the most respected institutions in Mexican society, ahead of Congress and the Roman Catholic Church.
Compulsory military service exists for all Mexican men above the age of 18, although in practice the majority are not required to serve.
For many poor Mexicans, however, joining the army remains a solid career opportunity, providing them with housing, education, health benefits and a minimum salary.
"I think that a young Mexican who decides to join the army is making one of the best decisions of his life," says Col Fidel Mondragon, head of training for new recruits at the Temamatla base near the capital.
But the army has lost some of its shine, analysts say.
According to a survey by polling firm Demotecnia, public approval of the army has dropped almost 20% since late 2006.
"There's been a radical change," says Maria de las Heras, head of Demotecnia. "The army is being seen through different eyes.
"People are starting to be afraid of the army when they see it patrolling the streets."
Some recent cases have fuelled these concerns.
Last March, two students in the northern city of Monterrey were killed as they were leaving their university campus.
Initially, they were said to have been caught in the crossfire between troops and alleged cartel members.
The army now has accepted a formal ruling by the National Commission of Human Rights that they were killed by troops who then tampered with the scene to cover their tracks.
In the last four years, the commission has received more than 4,200 complaints about alleged abuses, including accusations of rape, torture and excesses in their enforcement.
The army says it is investigating these cases and has strengthened soldiers' training in human rights.
It has also set up a special unit to engage better with the public.
The aim is to improve "the responsibility and assertiveness of the soldiers, to make the general public feel more at ease with their presence," the head of the unit, Marina Arvizu, told the BBC.
Some believe the government deployed the army too soon against the drug cartels, and without proper planning.
Four years on, it is not clear when or if the army will be able to declare victory in this battle.
"The results are mixed," says Raul Benitez Manaut, a defence expert at Mexico's National Autonomous University (Unam).
Several drugs lords have been captured and massive drug hauls recovered.
But Mr Benitez says: "The violence has increased to a level which is very hard for society to tolerate."
This year is already the bloodiest in the conflict: more than 10,000 people have been killed so far.
However, the government is adamant that the military option was the wisest and inevitable choice and it says withdrawing the troops at this point in the confrontation is not an option.
Inside the barracks, the new recruits seem ready to wage war.
"Here, they teach us to have courage," says Christian Andreu, who joined the army just a few weeks ago. "I'm not afraid."