In the 5th century A.D., Belarus (also known as White Russia) was colonized by east Slavic tribes. Kiev dominated it from the 9th to 12th century. After the destruction of Kiev by the Mongols in the 13th century, the territory was conquered by the dukes of Lithuania, although it retained a degree of autonomy. Belarus became part of the Grand Duchy of Lithuania, which merged with Poland in 1569. Following the partitions of Poland in 1772, 1793, and 1795, in which Poland was divided among Russia, Prussia, and Austria, Belarus became part of the Russian empire.

Following World War I, Belarus proclaimed itself a republic, only to find itself occupied by the Red Army soon after its March 1918 announcement. The Polish-Soviet War of 1918–1921 was fought to decide the fate of Belarus. West Belarus was ceded to Poland; the larger eastern part formed the Belorussian SSR, and was then joined to the USSR in 1922. In 1939, the Soviet Union took back West Belarus from Poland under the secret protocol of the Nazi-Soviet Nonaggression Pact and incorporated it into the Belorussian Soviet Socialist Republic. Occupied by the Nazis in World War II, Belarus was one of the war's most devastated battlefields.

When the Chernobyl nuclear power plant in Ukraine exploded in 1986, 70% of its radioactive fallout fell on the Belorussian SSR. Cancer and other illnesses have multiplied as a result.

Belarus declared its sovereignty in July 1990 and its independence in Aug. 1991. It became a cofounder of the Commonwealth of Independent States (CIS) in Dec. 1991. In Jan. 1994, the country's parliament ousted its reform-minded leader, Stanislav Shushkevich, in protest against his support for market economics. He was replaced by Alyaksandr Lukashenka, who, over the next two years, greatly expanded the powers of the presidency. Lukashenka sought to renew ties with Russia, and, with much fanfare, Belarus and Russia signed a treaty in April 1997 aimed at significantly increasing cooperation between the two states, stopping just short of union. The Russian financial crisis that began in fall 1998 severely affected Belarus's Soviet-style planned economy.

The EU and the U.S. have denounced the increasingly oppressive political atmosphere and human rights violations in Belarus under the Soviet-style authoritarianism of President Lukashenka. In 1999, the year Lukashenka was to step down, he rigged a national referendum allowing him to cancel the elections and remain president. Lukashenka's government has been accused of running a death squad that has killed dozens, including opposition party members and underworld figures. After harassing the opposition and curtailing their campaign activities, Lukashenka won reelection in the Sept. 9, 2001, presidential race. In 2004, the Council of Europe strongly criticized the Belarus government for blocking investigation into the disappearance of four dissidents in 1999 and 2000.

Presidential elections in March 2006 reelected Lukashenka with 83% of the vote. Supporters of opposition candidates took to the streets of Minsk to protest the results. The police cracked down on the demonstrations and arrested dozens. The U.S. and other Western nations declared the election fraudulent, and the EU imposed economic sanctions on Lukashenka and a number of his ministers.

Despite the close ties of Russia and Belarus, the two countries clashed over imported Russian gas in early 2007. In Dec. 2006, Russia doubled the price of gas it exported to Belarus, and then imposed a large duty on oil exports. In response, Belarus imposed a tax on Russian gas in Jan. 2007. Russia then shut off an oil export pipeline to Europe (which spelled trouble for Europe, since half of all European exports of Russian gas are transported through Belarus). By mid-January, Russia agreed to cut its oil duty and Belarus agreed to cut its tax.