Initially, Salazar was a professor of political economics at a Portuguese university. In 1932 he became Prime Minister of Portugal. Most historians consider dictatorship a more apt term for his rule. In 1933 he introduced a new constitution to Portugal. The constitution gave him almost unlimited powers, establishing an authoritarian fascist regime in Portugal.
Salazar was handed power by President Carmona in 1932 and gained major support from different elements of society. The anarchy of the republican era meant that the army, church, monarchists, upper middle classes, aristocrats and the right all preferred Salazar to the previous juntas.
Salazar developed the "Estado Novo" or new state. The basis of his dictatorship was a platform of stability. Salazar's reforms greatly privileged the upper classes to the detriment of the poorer sections of society. Education was not seen as a priority and therefore not expanded. Salazar had a version of the secret police named PIDE who repressed dissent. However unlike many of his contemporary dictators, Salazar's regime was less bloody due to Portugal's lack of a death penalty.
During World War II, Salazar steered Portugal down a middle path. Although a dictator and a supporter of Nationalist Spain (he sent them aid during their fight against the Republicans), like Franco he never sided with the Nazis. The Iberian neutrality pact was put forward by Salazar to Franco in 1939. Indeed Salazar provided aid to the Allies, letting them use the Azores as a base though he provided little else in the way of support. Siding with the Axis would have meant that Portugal would have been at war with Britain, which would have threatened Portuguese colonies.
In 1945 Portugal was in control of the Azores, Madeira, Cape Verde Islands, Principe Island, Sao Tome Island, Angola, Guinea-Bissau, Cabinda and Mozambique in Africa, Diu, Damao and Goa in India, Macau in China and East Timor in Southeast Asia. Salazar saw no need to expand the colonies just to ensure Portuguese control over them. The colonies formed the basis of Salazar's dependence upon the empire and national pride in Portugal's status as the 3rd colonial power.
Salazar wanted Portugal to be important internationally, and the country's large colonial holdings made this possible, while Portugal itself remained a closed state with little influence from the Western powers. Portugal was admitted to NATO in 1949 and this reflected Portugal's new role as an ally against communism.
From the Indian capture of Portuguese cities in 1961 and until after Salazar's death, the empire remained a continual source of trouble for Portugal, especially in the African colonial wars.
In 1968 Salazar decided to resign because of ill health. He died two years later.