Born into the large Rallis family, he studied Law and Political Science at the University of Athens. The declaration of the Greek-Italian War found him serving as a lieutenant in the Cavalry. He fought in the mountains of Northern Epirus in the 1st Reconnaissance Group and was distinguished for his bravery. He worked as a lawyer from 1941. He was involved in politics and was elected several times as a Member of Parliament of Athens, in all elections from 1950 to 1963. He served as Minister of the Presidency of the Government 1954-56, Minister of Communications and Public Works 1956-58, Minister of the Interior 1961-63 and again Minister of the Interior in 1967 when the military coup of the Colonels took place.
After the post-independence period of 1974, he was again elected several times as a Member of Parliament and became Minister of Interior in 1974, Minister of the Presidency of the Government 1975-77, Minister of National Education and Religious Affairs 1976-77 with great radical work for the educational reform and the introduction of the Modern Greek language at all levels of education and in the Public Administration with the abolition of the Katharevousa language. He then became Minister of Coordination and Foreign Affairs in 1978-80 and contributed to the acceptance of Greece as a 10th member of the European Union (EEC).
He was elected and succeeded Karamanlis in 1980 as leader of the New Democracy party and as Prime Minister of Greece until 1981. 1980 – 1981) He ended his parliamentary career in 1993.
He was a mild-mannered politician, a democrat and an evangelist. He was honoured by the State with the Order of Valour, the War Cross Third Class, the Medal of Exceptional Deeds, the Grand Cross of Honour, and Grand Crosses from France, Spain, Portugal, Thailand and Abyssinia.
He left an important and rich literary oeuvre, mainly of a historical and political nature. We selectively mention : Two Roads, The Truth about Greek Politicians, The Technique of Violence, Hours of Responsibility, Political Confessions, Looking back, Tade efi, To the ears of the inaudible, etc.