The long-running civil war in Colombia has left tens of thousands dead and has been described by the UN as one of the world's worst humanitarian crises.
The brutal conflict pits the state against two groups of left-wing rebels and some right-wing paramilitaries.
Insurgents launched campaigns to overthrow the government in the 1960s.
But since then, the armed groups have been drawn into kidnapping and the illegal drugs trade - producing nearly 80% of the world's cocaine.
The Revolutionary Armed Forces of Colombia (Farc) was officially formed in 1964, when it declared its intention to use armed struggle to seize power.
The smaller rebel group the National Liberation Army (ELN) was founded in 1965, inspired by the Cuban revolution.
The United Self-Defence Forces of Colombia (AUC) has its roots in the 1980s militias set up by drugs lords to combat rebel kidnappings and extortion.
This right-wing umbrella group is backed by elements in the army.
Civilians bear the brunt of the war. Three million have been displaced as armed groups bombard their villages, and subject them to massacres.
Those forced from their homes often suffer from hunger and poor health and are denied basic social services.
Indigenous groups say the war serves to hide the fact they have been driven off their land, which is endowed with natural resources like oil.
Colombia is rich in resources, but it is beset by poverty and unemployment.
The conflict has become intertwined with the illegal drugs trade, which finances both the Farc and the AUC.
Hundreds of US soldiers are in Colombia to help the government in its war against drug-smuggling and the rebels.
Since 2000, the US has funded a project called Plan Colombia. Forces receive training and equipment to root out smugglers and eliminate coca crops.
Hundreds of Colombian citizens have been extradited to the US to face trial for trafficking, under a two-way deal.
President Alvaro Uribe has made national security his main goal.
He has sought to confront the Farc head on, and many war-weary Colombians have welcomed his achievements in pushing the conflict back into the countryside.
Negotiations with the AUC have resulted in the demobilisation of several thousand of their fighters.
But critics say Mr Uribe's tactics have led to human rights abuses and have done little to reduce the violence, while neglecting social development.