One persistent problem is that in many of the partner nations, police are so institutionally weak or corrupt that governments have turned to their militaries to fight drug traffickers, often with violent results. Militaries are trained for combat, while police are trained to enforce laws.
"It is unfortunate that militaries have to be involved in what are essentially law enforcement engagements," said Frank Mora, the outgoing deputy assistant secretary of defense for Western Hemisphere affairs. But he argues that many governments have little choice.
Mora said the effort is not tantamount to militarizing the war on drugs. He said the Defense Department's role is limited, by law, to monitoring and detection. Law enforcement agents, from the U.S. Coast Guard, Customs and Border Protection or other agencies are in charge of some of the busts, he said.
But the U.S. is deploying its own military. Not only is the Fourth Fleet in the Caribbean, the Pacific and the Atlantic, but the Marines were sent to Guatemala last year and the National Guard is in Honduras.
The Obama Administration sees these deployments as important missions with a worthy payoff. Hundreds of thousands of kilograms (pounds) of cocaine are seized en route to the U.S. every year, and the Defense Department estimates about 850 metric tons of cocaine departed South America last year toward the U.S., down 20 percent in just a year. The most recent U.S. survey found cocaine use fell significantly, from 2.4 million people in 2006 to 1.4 million in 2011.
Aboard the Underwood, the crew of 260 was clear on the mission. The ship's bridge wings bear 16 cocaine "snowflakes" and two marijuana "leaves," awarded to the Underwood by the Coast Guard command to be "proudly displayed" for its successful interdictions.
Standing on the bridge, Carpio's team spotted its first bale of cocaine. And then, after 2 1/2 weeks plying the Caribbean in search of drug traffickers, they spotted another, and then many more.
"In all we found 49 bales," Carpio said in an interview aboard the ship. "It was very impressive to see the bales popping along the water in a row."
Wrapped in black and white tarp, they were so heavy she could barely pull one out of the water. Later, officials said they'd collected $27 million worth of cocaine.
The current U.S. strategy began in Colombia in 2000, with an eight-year effort that cost more than $7 billion to stop the flow from the world's top cocaine producer. During Plan Colombia, the national police force, working closely with dozens of DEA agents, successfully locked up top drug traffickers.
But then came "the balloon effect."
As a result of Plan Colombia's pressure, traffickers were forced to find new coca-growing lands in Peru and Bolivia, and trafficking routes shifted as well from Florida to the U.S.-Mexico border.
Thus a $1.6 billion, 4-year Merida Initiative was launched in 2008. Once more, drug kingpins were caught or killed, and as cartels fought to control trafficking routes, increasingly gruesome killings topped 70,000 in six years.
Mexican cartel bosses, feeling the squeeze, turned to Central America as the first stop for South American cocaine, attracted by weaker governments and corrupt authorities.
"Now, all of a sudden, the tide has turned," said Brick Scoggins, who manages the Defense Department's counter-narcotics programs in most of Latin America and the Caribbean. "I'd say northern tier countries of El Salvador, Honduras, Guatemala and Belize have become a key focus area."
The latest iteration is the $165 million Central America Regional Security Initiative, which includes Operation Martillo (Hammer), a year-old U.S.-led mission. The operation has no end date and is focused on the seas off Central America's beach-lined coasts, key shipping routes for 90 percent of the estimated 850 metric tons of cocaine headed to the U.S.
As part of Operation Martillo, 200 U.S. Marines began patrolling Guatemala's western coast in August, their helicopters soaring above villages at night as they headed out to sea to find "narco-submarines" and shiploads of drugs. The troops also brought millions of dollars' worth of computers and intelligence-gathering technology to analyze communications between suspected drug dealers.
Assistant Secretary of State William Brownfield, head of the Bureau of International Narcotics and Law Enforcement Affairs, predicts the balloon effect will play out in Central America before moving to the Caribbean.