The conflict in the Democratic Republic of Congo has caused more deaths than any war since World War II - some 3.3 million between 1998 and 2002 alone.
Sporadic fighting continues despite a peace agreement and the creation of a power-sharing government in 2003.
DR Congo is a vast country, two-thirds the size of Western Europe, with a population of 50 million.
Its diamonds and minerals should have made it rich - but they have tempted outsiders to grab land and plunder it.
DR Congo's current troubles stem from the 1994 Rwanda genocide.
After butchering 800,000 people, the killers fled across the border into DR Congo (then known as Zaire).
Rwanda's new leaders wanted the Congolese dictator, Mobutu Sese Seko, to disarm the militias and were prepared to use force to get their way.
First they sent troops and engineered a rebellion to topple Mobutu. Then they invaded again in 1998 in an attempt to oust his successor, Laurent Kabila.
Rwanda, Uganda, Burundi and Congolese rebels fought against President Kabila's government, while Zimbabwe, Angola, Namibia came to his defence.
The UN accused the warring parties of deliberately prolonging the war as they looted gold, diamonds and other goods.
The murder of Laurent Kabila in 2001 and the succession of his son, Joseph, helped speed up moves towards peace.
Donors warned Rwanda and Uganda to pull out or risk losing aid. Most foreign troops finally left in 2002.
A deal to end the fighting led to the creation of a transitional government in April 2003.
Rebel leaders got seats in government, it was agreed their forces would form a united national army and elections were scheduled for 2005.
Some of the three million left homeless by the war began to return home.
However, violence continues in the north and east of the country, where thousands of UN peacekeepers are struggling to contain ethnic tensions.
The most volatile areas of DR Congo are Ituri, on the Ugandan border, and North and South Kivu, near Rwanda.
In Ituri, where Uganda's influence is strong, the Lendu and Hema ethnic groups are at war.
In the Kivus, a former rebel militia with close links to Rwanda is the dominant force. Dissident units have clashed with loyal government forces.
These conflicts strain DR Congo's ties with its neighbours, and deepen rifts within the transitional government.
The war in DR Congo disrupted trade and farming, adding to economic woes caused by decades of dictatorship.
Mobutu looted billions of dollars from the country during his 26 years in power, but left it without proper road, rail or telephone systems.
Hyperinflation and shortages of basic goods followed under Laurent Kabila.
The theft of resources continues, while DR Congo still lacks the infrastructure to provide its people with food, clean water, health care and education.