Following is a timeline of the key events in the U.S. war on drugs in Latin America.
1970 - The United States passes laws prohibiting narcotics use under the Controlled Substances Act.
1971 - U.S. President Richard Nixon declares a war on drugs and says drug abuse is the country's biggest threat.
1973 - Nixon sets up the Drug Enforcement Administration, or DEA.
1975 - Drug gangs kill 40 people in one weekend in the Colombian city of Medellin after police seize 1,320 pounds (600 kgs) of cocaine in one of the first ever big drug hauls.
1981 - Drug lord Pablo Escobar forms the Medellin Cartel with other powerful Colombian traffickers. The cartel begins to move tons of cocaine into the Miami via the Caribbean.
1982 - Escobar briefly wins a seat in Colombia's Congress as he cuts a Robin Hood figure in Medellin, giving out money in slums and building houses for the poor.
1984 - Drug hitmen kill Colombia's justice minister. Escobar is indicted for the murder and flees to Panama. The DEA and Colombian police uncover a massive cocaine production facility deep in the jungle.
1985 - Cocaine smuggling shifts into Mexico after U.S. law enforcement cracks down on maritime smuggling into Miami. The godfather of Mexican narcotics trafficking, Miguel Angel Felix Gallardo, pioneers smuggling routes to the United States for Colombian cartels.
1989 - Mexican police and the DEA arrest Felix Gallardo. His nephews Benjamin, Ramon and Javier Arellano Felix gradually take over his business, moving up to Tijuana on the U.S. border from their home state of Sinaloa to smuggle tons of cocaine into the lucrative Californian market.
1993 - Colombian police with U.S. help track down Escobar and kill him. With the Medellin cartel dismantled, a group of traffickers from the Colombian city of Cali rise in power.
1996 - Colombia police and the DEA dismantle the Cali cartel. In Mexico, smuggler Osiel Cardenas takes over the Gulf Cartel on the Texas border. He later recruits elite soldiers in Mexico's army to form the cartel's feared armed wing, the Zetas.
2000 - U.S. President Bill Clinton gives Colombia $1.3 billion in aid under Plan Colombia.
2001 - Joaquin "Shorty" Guzman, escapes from a Mexican prison in a laundry van. Mexico's most-wanted drug lord, he heads a coalition of drug gangs from Sinaloa state and vows after his escape to take control of Mexico's $40 billion-a-year drugs trade.
2002 - Mexican police kill Ramon Arellano Felix in Sinaloa and weeks later arrest his brother Benjamin. Rival gangs try to muscle in on the weakened Tijuana cartel.
2006 - Mexican President Felipe Calderon sends tens of thousands of troops and federal police across Mexico to try to stem growing drug violence sparked by Guzman's territorial ambitions.
2007 - Mexico extradites Gulf Cartel kingpin Cardenas to the United States and makes a historic 23-tonne cocaine seizure. U.S. President George W. Bush pledges a $1.4 billion anti-drug package for Mexico and Central America. But the violence escalates.
2008 - Mexico captures hundreds of drug gang members, disrupting smuggling routes but unleashing yet more violence. Some 6,000 people are killed across Mexico as rival gangs fight each other and security forces in the worsening drug war.
(Reporting by Robin Emmott in Monterrey; Editing by Kieran Murray)