Pygmies, migrating from the Congo (Kinshasa) region, were probably the first inhabitants of what is now the Republic of the Congo. Other early inhabitants include the Bakongo, the Bateke, and the Sanga, who arrived in the 15th cent. After the coastal areas were explored by the Portuguese navigator Diogo Cão in 1482, commerce developed between the Europeans and the coastal African states, which raided the interior for slaves to trade.
Portuguese traders predominated throughout the 17th cent., although French trade centers were established (mainly at Loanga), and English and Dutch merchants sought commercial opportunities. Europeans penetrated inland in the late 19th cent., with Pierre Savorgnan de Brazza leading major expeditions in 1875 and 1883. In 1880 he negotiated an agreement with the Bateke to establish a French protectorate over the north bank of the Congo River.
Between 1889 and 1910, the Congo (called the French Congo and later the Middle Congo) was administered primarily by French companies that held concessions to exploit the area's rubber and ivory resources. Scandals over the decimation of the African population through forced labor and porterage broke out in 1905 and 1906. France restricted the role of the concessionaires in 1907, and in 1910 the Congo became a colony in French Equatorial Africa. Renewed forced labor and other abuses sparked an African revolt in 1928. The Free French forces made the Congo a bastion of their struggle against the Germans and the Vichy regime during World War II. In 1946, the region was granted a territorial assembly and representation in the French parliament. In the French constitutional referendum of 1958, the Congo opted for autonomy within the French Community.
Full independence was achieved on Aug. 15, 1960, with Fulbert Youlou as the first president. Forced to resign after a revolt in 1963, he was succeeded by Alphonse Massamba-Débat. In 1964 the new president founded a Marxist-Leninist party and proclaimed a noncapitalist path of economic development. A Five-Year Plan was initiated, and the state sector of the economy in agriculture and industry was expanded. Tensions between the government and the army grew, and in 1968, Marien Ngouabi, an army commander, seized power. He followed his predecessor's socialist policies but created his own Marxist-Leninist party, the Congolese Workers party (PCT). An attempted coup in 1972 provided Ngouabi with a reason to purge opponents. Ngouabi was assassinated in 1977 after being unable to contain the growth of the popular opposition movement.
The success of the Marxist party in Angola led to imitation in the Congo and Ngouabi's successor, Joachim Yhombi-Opango, was expected to reestablish military control over the PCT. He instead attempted to dissolve the PCT congress, a move that the trade unions protested. Amid accusations that he had embezzled government funds, Yhombi was ousted from the PCT and in 1979 Col. Denis Sassou-Nguesso was appointed head of state.
Sassou-Nguesso maintained a politically neutral course in international affairs, seeking ties with both capitalist and Communist countries (the Congo signed a treaty of friendship with the Soviet Union in 1981, as it continued to benefit from French investment). A dramatic decline in petroleum prices resulted in severe unemployment in 1988 and 1989. The PCT-appointed congress reelected Sassou-Nguesso president for a third five-year term in 1989.
In 1992, voters approved a new constitution establishing multiparty rule, and Pascal Lissouba won the country's first democratic presidential election. However, disputed parliamentary elections in 1993 led to bloody fighting between progovernment forces and the opposition (both largely ethnically based groups). Following a Jan., 1994, cease-fire, tribal militias began disarming; the following year some opposition members were included in the government. Unrest continued, however, with full-scale civil war breaking out in June, 1997. Presidential elections scheduled for July were cancelled, and by October the forces of Sassou-Nguesso, aided by Angolan troops, had captured Brazzaville, and Lissouba had fled the capital. Sassou-Nguesso was installed as president, but fighting continued into 1999, when a cease-fire was signed.
In the Pool region in the south, however, fighting erupted with rebel militias in 2002–3; a new peace deal did not lead to disarmament as intended. The militias remain in control in some areas in the south and have turned to criminal activities to support themselves; fighting broke out in the capital in Oct., 2005. Meanwhile, in Mar., 2002, Sassou-Nguesso was elected to a seven-year term as president, but the vote was marred by irregularities. A new peace accord was signed with the Pool region rebels in Apr., 2007, and the following month their leader was given a post in the government. Legislative elections in mid-2007 were won overwhelmingly by parties allied with the president; most opposition parties boycotted the polls, which were criticized by many observers. Sassou-Nguesso was reelected in July, 2009, in balloting that was boycotted by some in the opposition and was reported to suffer from a low turnout (despite official figures of 66%). In mid-2012 the governing party and its allies again won a majority in the legislative elections.