The United States has increased the amount spent on helping to train Mexico's armed forces by a factor of five since 2009, from $3 million annually to $15 million in 2014.

This quiet increase is meaningful because historically Mexico has been among the countries in the Western Hemisphere most reluctant to cooperate with US armed forces.

Part of the reason is that Mexico has always been somewhat sensitive to the perception they are dependent on American help. But more and more Mexicans now are being trained at US military bases.

In a statement to Fox News Latino, US Northern Command, which oversees the United States' military relationship with Mexico, said that in 2013 the US "had more than 150 engagements, sharing training opportunities with more than 3,000 Mexican soldiers, sailors, airmen, and Marines."

Those opportunities include training in aviation, search and rescue missions, leadership, combat medicine, urban operations, small-unit tactics, helicopter maintenance, and even English-language lessons. The statement added that the US "regularly participates in mutual exchanges with the Mexican military such as attending each other's professional military schools and visiting military headquarters."

"We have made the effort to try and share many of the lessons we've learned in chasing terrorist organizations in Iraq and Afghanistan," said retired US Northern Command General Victor Renuart.

US Northern Command says it's too soon to be able to tell what the budget for such engagements will be for next year, but the trend over the last few years suggests it will be even higher.

Of course, $15 million is not that much when you compare it to the $2.1 billion Merida Initiative started in 2008. The initiative is the cornerstone of US-Mexico security cooperation to help fight violence and organized crime in Mexico, Central America, the Dominican Republic, and Haiti.