Under Prime Minister Winston Field, Smith served as deputy prime minister and minister of the Treasury (1962-1964). When Field was ousted by rightists in his party on April 13, 1964, Smith became prime minister. He also served as minister of defense (1964-1965) and as minister of external affairs (1964).

Smith's rise to leadership fitted Southern Rhodesia's political history. White settler occupancy of the territory had begun in 1890. The settlers received self-governing status in 1923; Britain retained only veto power over legislation discriminatory to Africans. Continuation of minority white rule, critics believed, lay behind the formation of the ill-fated Federation of Rhodesia and Nyasaland (1953-1963). Smith rose to power because of his firm white supremacist stand at a time when African countries to the north were gaining independence under black rule and when Britain was pressing for constitutional changes enabling unimpeded progress toward African majority rule. Smith represented 240,000 whites determined to control a country in which 4.5 million Africans also lived.

On black-white relations, Smith quoted his father as saying, "We are entitled to our half of the country and they are entitled to theirs." Friendly Rhodesians referred to Smith as "Iron Man Ian" or "Good Old Smithy." Critics called him the world's foremost white supremacist. His wife said of him, "No one can influence my husband once he has made up his mind."

Smith's goal was to negotiate independence for Rhodesia under the 1961 Constitution (the name was shortened after Northern Rhodesia became independent as Zambia on Nov. 24, 1964). British prime minister Harold Wilson would not agree without guarantees of unimpeded African progress toward majority rule. Frequent talks in London and Salisbury did not resolve the impasse. Smith was under pressure from whites who were even more extreme than his own government.

On Nov. 11, 1965, Smith issued a declaration of independence reminiscent of the American colonial revolt in 1776. Britain retaliated by cutting off Rhodesia from the sterling trade area, dismissing the Smith government, invalidating Rhodesian passports, and banning purchases of Rhodesia's cash crop of tobacco. Wilson declared that he would not use force to bring Rhodesia to heel. On Dec. 16, 1967, the United Nations Security Council joined Britain's earlier move in imposing economic sanctions against Rhodesia. Despite discomfort from the shortages of some luxuries, Rhodesia received petroleum products and other vital items from the Republic of South Africa, Portuguese Mozambique, and other sources.

Fruitless talks took place between Smith and Wilson on British ships off Gibraltar in 1966 and 1968. In a constitutional referendum on June 20, 1969, Smith's government received a 72 percent vote approval for a new constitution aimed at legislative parity between whites and Africans when income tax parity was reached (that is, very slowly). He also received an 82 percent vote approval for republican status. On March 1, 1970, Smith declared Rhodesia a republic, severing all ties with Britain.

Urged by Britain, the UN voted to impose economic sanctions against Rhodesia, and African nationalist factions began mobilizing increasingly powerful guerrilla forces in nearby Zambia against the illegal government. In 1973, Smith closed the border with Zambia, causing significant damage to the Rhodesian Railways, which depended on Zambian copper ore.

The civil and guerrilla war escalated in 1975 after the independence of Mozambique opened another base for guerrilla operations. Whites began to flee the border regions as the war continued, adding to the economic hardships imposed by sanctions and the worldwide oil crisis. In the face of diminishing support and supplies from South Africa and increasing international pressure, Smith announced in 1977 that he would enact majority rule in Rhodesia within two years. Later that year he publicly accepted the principle of universal suffrage.

In March, 1978, Smith reached an agreement with African nationalist leaders to set up an executive council while retaining his power in a first step toward majority rule. In 1979 he accepted a shared government with Abel Muzorewa, whose party won the first universal suffrage election in Rhodesian history. Rhodesia was renamed "Zimbabwe Rhodesia," and Muzorewa replaced Smith as prime minister in June 1979. In 1980, Zimbabwe achieved independence from Great Britain under a consitution that guaranteed Europeans 20 out of 100 seats in the national assembly. Robert Mugabe, who had waged a guerrilla campaign, easily won the 1980 elections and established the first free African government in Zimbabwe.

Smith continued to serve in the Parliament as leader of the Republican Front until 1987, when he was suspended. His influence diminished as other RF party members sought to support the Mugabe regime, but he continued to criticize the government and rallied opposition to Mugabe in the 1995 elections.

In his memoirs, The Great Betrayal, Smith continued to assert that the black majority should be "gradually" raised to the "standards of Western civilization" and discussed black "terrorists" while downplaying the cruelties of Rhodesia's armed forces during the civil war. He asserted that Britain hypocritically imposed sanctions on Rhodesia even though many of its other states had one-party governments. His own account also emphasized the dictatorial nature of the Mugabe regime and its resistance to democratic reforms. Since leaving politics, Smith has lived on his farm in Zimbabwe