- Guinea-Bissau won independence from Portugal in 1974.
- Luis Cabral became president in 1974, ousted in 1980 coup led by armed forces chief Joao Bernardo Vieira.
- Vieira clung to power despite alleged coup attempts, was elected president in 1994 multi-party polls.
- Bloody civil war in 1998 after an army uprising.
- Military junta ousted Vieira in 1999; opposition leader Kumba Yala elected president in 2000.
- President Yala ousted in bloodless military coup in 2003; Businessman Henrique Rosa sworn in as president.
- Joao Bernardo Vieira won 2005 presidential vote and was killed by soldiers in the presidential palace in 2009.
- Malam Bacai Sanha elected president and while hospitalized in 2011 a military struggle and attempted coup took place.
- President Sanha died in January 2012 after a long illness; National Assembly Speaker Raimundo Pereira became acting president.
Guinea-Bissau is headed toward a presidential run-off election after no candidate won a majority in Sunday's first-round voting.
Official provisional results released Wednesday showed former prime minister Carlos Gomes Jr. barely missed an outright victory, taking just under 49 percent.
Gomes, the ruling party candidate, will now face opposition leader and former president Kumba Yala, who came in second with 23 percent.
Yala is one five candidates who on Tuesday called for the election to be annulled because of alleged fraud. The candidates said the election lacks credibility because it was rife with irregularities.
International election observers have said Sunday's poll appeared to be free and fair.
The fraud claims have raised fears that trouble is looming in the coup-prone country, where former military intelligence chief Samba Diallo was killed hours after the polls closed.
The winner of the run-off will replace the late president Malam Bacai Sanha, who died in January after a long illness.
While Sanha was hospitalized in December, a struggle within the military and an apparent coup attempt took place.
Since winning independence from Portugal in 1974, Guinea Bissau has struggled through a dictatorship, three coups and the 2009 assassination of a president.
The country has also become a transit point for cocaine smugglers.
Some information for this report was provided by AP, AFP and Reuters.