He studied at the Evelpidon School. He fought in Albania as a Lieutenant. He fled to the Middle East and joined the Iero Company, fought as a lieutenant in the operations of the East. He served as a lieutenant in the Aegean Sea. In 1944 he entered the liberation army in Athens. He fought in Korea. He was an instructor at the Evelpidon School. Commander of a Commando Squadron. Founder and Director of the Parachute School (1955-59).

As a Brigadier General in 1967, he did not accept the dictatorship of the Colonels and was dismissed from the army. He was exiled and imprisoned in Serifos, Samothrace and Thermo Trichonis. In 1976 he went to the USA where he attended a series of university training seminars in sociology, business administration, political science and international relations.

He returned to Greece and was appointed (unpaid) as President of the General Bank, the Army Stock Fund, NIMITS and the Post Office. He was also vice-president of the Athenian Club and President of the New Democracy . Papathanasiou was honored for his bravery and patriotism 34 times with medals, decorations and distinctions from his country and from the United Nations, USA, Korea, six of them were Gold Medal of Valour.