IOAN GRILLO: Deep in the Sierra Madre Mountains, this beautiful landscape in northwest Mexico hides one of the world's biggest drug-producing areas, the so-called Golden Triangle.
In a rare opportunity, we joined the 94th Battalion to see its work fighting drug cartels here. Battalion Commander General Solorzano says it is the only force equipped for this job. As we fly low, soldiers watch for cartel snipers, who have targeted army helicopters with machine guns and even rocket-propelled grenades.
The soldiers have located a marijuana field, which sticks out because of the bright green leaves of the plants. We touch down and head to the crop. The troops are constantly on guard for enemy fire. In the last 18 months, cartel hit men have slain more than 1,000 soldiers and police officers.
The general explains that there are about 25,000 square feet of plants here, or enough for 500 pounds of grass for American smokers.
GEN. FEDERICO EDUARDO SOLORZANO, Mexican Army: To make their marijuana joints, they use the so-called sheep tails. If you touch it, you can feel that it is sticky. Touch it.
IOAN GRILLO: This is a small crop by Mexican standards. The plants tear from the ground easily. And, within two hours, the soldiers have ripped up the entire field and burned it on a bonfire.
The Mexican government has also sent troops into city centers to fight the drug war. We follow the soldiers on one of these urban operations. The unit sets up impromptu checkpoints which are moved every hour. In this Mustang, they find a stash of firearms in the front seat. But it turns out the driver is a police detective, and they let him go.
MAJ. ENRIQUE ELVIRA SAENZ, Mexican Army: We see people who are very ostentatious. They show off their gold chains, big bracelets. But then they wear leather sandals. And these are things that give them away.
IOAN GRILLO: The army also sifts through residential neighborhoods searching for gangsters. Troops say this molecular device can detect firearms or drugs at 300 yards. But many residents don't like the military invading their lives.
MOREIMA COMPOMANES, businesswoman: Why do you do this to us?
IOAN GRILLO: This businesswoman gets annoyed about being stopped on her own street and launches into a scathing attack on the soldiers.
MOREIMA COMPOMANES: How much longer will we citizens have to put up with you stopping us. Look, one night I was with two friends who live two blocks away. They were all my age, grandparents. They stopped us here. They stopped us there, then on the corner, then again outside the house. Please. Four checks in five minutes, how can this be?
IOAN GRILLO: Many Mexicans complain that the army operations have not stopped the violence and trafficking. This month, the military has also come under fire for human rights abuses, accusations it promises to investigate.
But the government insists, if the troops were sent back to their barracks, the situation would only get worse. And, as the conflict intensifies, there is no sign of them leaving the frontline anytime soon.