In a cable dated Jan. 29, John Feeley, the deputy chief of mission for the U.S. Embassy in Mexico City, praised the Mexican marines and said that "our ties with the military have never been closer in terms of not only equipment transfers and training, but also the kinds of intelligence exchanges that are essential to making inroads against organized crime." The cable was written before a high-level Defense Bilateral Working Group meeting in Mexico in February.

The diplomat wrote that "for the first time," the Mexican army is "following the Navy's lead" and "has asked for SOF training." SOF is an acronym for Special Operations Force.

Another example shows the U.S. involvement in the killing of Arturo Beltran Lleyva (background here.)

In another cable, after a December 2009 operation that resulted in Beltran Leyva's killing in a luxury condo in Cuernavaca, U.S. Ambassador Carlos Pascual also praised the marines corps for "its emerging role as the key player in the counter-narcotics fight."

According to the ambassador, the marine unit that led the operation had been "extensively trained" by the U.S. Northern Command, the Pentagon's joint operations center in Colorado that oversees and coordinates defense in North America, including Mexico.

The DEA feeds intelligence to the Mexican military which sends the Navy or Marines in for the takedown and kill.

"They are working almost exclusively on our intel," said a senior U.S. official who spoke on the condition of anonymity for fear of upsetting nationalist sensitivities here.

The U.S. official described the training as QRF - Quick Reaction Force training - consisting of "light armored infantry training, with small unit operations in urban settings, and tactical maneuvering."

This is all with the blessing of the U.S. Congress:

Congress has set aside at least $310 million for the Mexican navy since 2007, including surveillance planes and Black Hawk helicopters, as part of the $1.6 billion Merida Initiative, according to the Washington Office on Latin America, which tracks military aid to the region.

The U.S. prefers the Navy to the Army:

In one of the leaked cables, U.S. diplomats refer to the Mexican army as parochial, risk-averse and jealous of its turf and privileges. In contrast, Mexican navy officers have been working with American and other foreign counterparts for years, developing a degree of trust enjoyed by no other Mexican force.

Some of the cables are printed here.