Origin of the conflict
When a populist political leader was assassinated in 1948, an urban riot killing evolved La Violencia, ten years of rural warfare between members of Colombian Liberal Party and the Colombian Conservative Party. After this civil war, most self-defense and guerrilla groups ceased to exists, but some Liberal and Communist groups continued. The war ended with the National Front, an agreement between the Liberal and Conservative parties to rule alternately. This left no room for other parties. The social inequity and the political exclusion are the main causes the groups continued to fight.

Chronological timeframe
In 1958 the civil war ended, and though most armed parties ceased to exist, some continued to fight. During the ‘80s, the trade in narcotics grew. This provided guerrilla groups with more means to finance their strife. Paramilitary groups came into existence in the ‘90s, they were helping the army. After it became apparent that these groups were violating human rights and causing many civilian casualties, they were banned. They still exist under the AUC, but the government has initiated a demobilisation process of the paramilitary groups.

Actors involved
-The Colombian government, headed by President Alvaro Uribe Vélez, which attempts to vanquish the armed troops and fight drug trade.
-FARC and ELN are two different guerrilla groups fighting against the social-economic inequity in Colombia. In order to achieve their goals they attack citizen and military targets and they finance themselves by means of kidnapping and drug trade.
-AUC heads all paramilitary groups in the country. Apart from protecting their main sponsors, they also attack citizens as well as the military and use kidnappings to provide for extra finances.
-The US supports Colombia in its war on drug trade and armed groups, as the drugs on US markets come mainly from Colombia.

Response of the international community
The international community supports the Colombian government in its attempt to restore law and order in the country and to find a solution for the armed conflict. The US’ supported ‘Plan Colombia’ has a military character and involves fighting against the guerrilla groups and the ruining of illegal crops, by spraying insecticides from airplanes on the fields.It is therefore often criticised.

Sources
http://en.wikipedia.org/wiki/Colombian_armed_conflict_(1964%E2%80%93present)
Stokes, Doug, America's Other War: Terrorizing Colombia (2005)
http://news.bbc.co.uk/2/hi/americas/1738963.stm