Q&A: Mexico's drug-related violenceContinue reading the main story
In December 2012, Enrique Pena Nieto was sworn in as Mexican president, succeeding Felipe Calderon who had launched a crackdown on the drug gangs six years earlier.
Mr Pena Nieto had campaigned on a promise to to switch the focus from tackling the gangs and hunting drug barons to reducing the crime and violence that affect the lives of Mexicans.
What is the scale of the violence?
Keeping track of the drug deaths is difficult, as official figures have been issued sporadically. Most estimates put the number of people killed in drug-related violence since late 2006 at more than 60,000. Although there is no official breakdown of the numbers, the victims include suspected drug gang members, members of the security forces and those considered innocent bystanders. However, analysts have tracked an overall reduction in violence during 2012, continuing a trend from the previous year.
Where are the worst-hit areas?
Violence was first concentrated in Mexico's northern border regions, especially Chihuahua, as well as Pacific states like Sinaloa, Michoacan and Guerrero. Ciudad Juarez (just across from El Paso in Texas) was the most violent city. In 2010, some 3,100 people were killed in Juarez, which has a population of more than a million. Violence has now dropped markedly in Juarez.
However, Guerrero, home to the resort of Acapulco, as well as Sinaloa and Nuevo Leon remain among some of the most violent regions. One of the focal points for violence since 2010 has been Mexico's third-largest city, Monterrey.
2011 also saw new areas hit. For example, Veracruz on the eastern coast saw a series of mass killings.
Who are Mexico's powerful cartels?
The cartels control the trafficking of drugs from South America to the US, a business that is worth an estimated $13bn (£9bn) a year. Their power grew as the US stepped up anti-narcotics operations in the Caribbean and Florida. A US state department report estimated that as much as 90% of all cocaine consumed in the US comes via Mexico.
Alliances shift between the main gangs as they vie for control of trafficking routes. Experts argue that there are now two main players: the Sinaloa (also known as the Pacific) Cartel and Los Zetas. US security firm Stratfor, in a January 2012 report, said that Los Zetas were the biggest cartel in terms of geographic presence.
However, analysts believe Los Zetas have now split into two rival factions. One side is led by Miguel Angel Trevino, a former member of the Gulf Cartel. The other leader is a former soldier from an elite army unit, Heriberto Lazcano. The Mexican authorities confirmed on 9 October that Lazcano had been been killed in a shootout with marines.
What has been Mexico's strategy to tackle drug-trafficking and violence?
Former President Calderon deployed more than 50,000 troops and federal police against the cartels. Many of the main gang leaders were either arrested or killed. The Calderon administration argued that the violence showed that this aggressive strategy was forcing gangs to split and take on one another, often in increasingly brutal and gruesome fashion.
But hasn't there been concerns about the military's involvement in the drugs war?
Human rights activists have expressed concern that troops are ill prepared for policing duties. The military's lack of accountability is also an issue, as soldiers have been subject only to military justice. In July 2011, the Supreme Court ruled that soldiers should be tried in civilian courts.
How serious is corruption within the police?
Very. One reason why the federal government deployed the army and marines so extensively is that it felt the police could not be trusted. Drug cartels with massive resources at their disposal have repeatedly managed to infiltrate the underpaid police, from the grassroots level to the very top. Efforts are under way to rebuild the entire structure of the Mexican police force, but the process is expected to take years.
So what is President Pena Nieto's drugs strategy?
Look for a change in emphasis rather than overall direction to the Calderon approach. On 17 December, Mr Pena Nieto began to fill in some of the details. He announced the setting up of a national gendarmerie, initially 10,000 strong, that will take over from the troops on the ground and focus on law enforcement. The federal police will also be boosted to focus on investigations. However, he gave no timeframe for this.
To what extent is violence spilling into the US?
Most of the violence remains firmly on the Mexican side of the border, according to an August 2011 report by the US National Drug Intelligence Center.
The report said that major Mexican-based transnational criminal organisations (TCOs) would continue to dominate wholesale drug trafficking in the US for the foreseeable future and will further solidify their positions through collaboration with US gangs.
What has been the US response to the drug trafficking and violence?
In March 2009, the US government announced that it would step up efforts to disrupt the illegal flow of weapons and drug profits from the US to Mexico - a key demand of the Mexican government.
However, in November 2010, a US justice department report said that US efforts to tackle gun-smuggling lacked focus, with not enough intelligence-sharing between US agencies and with their Mexican partners.
And a Senate report in June 2011, Halting US Firearms Trafficking to Mexico, suggested that some 70% of firearms recovered from Mexican crime scenes in 2009 and 2010 and submitted for tracing came from the US.
The US, Mexico, Central American nations, Haiti and the Dominican Republic form the Merida Initiative - a $1.5bn scheme that aims to help by providing equipment and training to support law enforcement operations.