Mexico sent in the army to fight the drug war. Many question the toll on society and the army itself

MEXICO CITY - The handwritten letter addressed to the Mexican president and lawmakers came from a military prison outside the capital.

Its authors were 20 soldiers awaiting sentencing for crimes committed during Mexico's drug war, which has seen tens of thousands of troops deployed against well-armed criminal gangs in a bloody conflict without apparent end.

"We ... were used by the Mexican state in a failed experiment which resulted in an enormous number of collateral victims and dozens of soldiers of low rank in prison," the jailed troops wrote. "We are performing a function for which we were not prepared."

The missive was a rare public expression of disquiet from members of Mexico's insular military. The plea captured what some call a growing sense of unease and even dissent as Mexico moves toward what appears to be a permanent use of troops in its war on drugs.