Born in 1922 in the village of Dafni, Phthiotis, he enrolled in the Hellenic Army Academy in 1939.
Following the German invasion of Greece and the occupation of the country, he fled to the Middle East where he joined the armed forces of the Greek government in exile, first in the ranks of the 2nd Greek Brigade and then in the Sacred Squadron special forces unit, with which he fought in the Western Desert and Tunisia Campaigns, as well as in operations against the German garrisons of the Aegean islands.
With the restoration of democracy in 1974, he was recommissioned and eventually retired as a major general.
Despite his own career in the arch-conservative special forces, and his family's royalist background, he became a close friend of the founder of the Panhellenic Socialist Movement, Andreas Papandreou, whose head of security he was.
When Papandreou became the country's first socialist prime minister in 1981, Drossoyannis greatly helped in effectively controlling the largely conservative Greek officer corps.