Olusegun Obasanjo (ōlōō´shĕgōōn ōbā´sănjō), 1937–, Nigerian military officer and political leader, b. Abeokuta. Obasanjo, who joined the army in 1958 and rose quickly to general, was a key commander during the secession of Biafra (1967–70). He was Gen. Murtala Muhammad's deputy during his presidency, and succeeded him when Muhammad was assassinated in 1976. In 1979, Obasanjo voluntarily stepped down after the election of President Shehu Shagari. A vocal opponent of Sani Abacha's military dictatorship in the early 1990s, Obasanjo was jailed in 1995 and released after Abacha's death in 1998. He became leader of the dominant People's Democratic party and was elected president in 1999, ending 16 years of military rule. Obasanjo announced that he would fight corruption and improve the economy. These goals have only been partially achieved at best, and Nigeria has struggled with renewed ethnic and religious strife. He was reelected in 2003, but the election was marred by vote rigging. His reputation was further tarnished by his subsequent attempts to change the constitution to permit a third presidential term and to thwart his vice president from running for president and by the blatant fraud in the 2007 presidential and legislative elections. He was succeeded (2007) as president by Umaru Yar'Adua. Subsequently, various government bodies investigated possible corruption involving Obasanjo, his family, and his associates.