Petros Klados was born in Piraeus in 1879,[1] and entered the Hellenic Army Academy, graduating as an infantry second lieutenant on 11 July[2] 1901.
[3] He continued his education at the in France at the École supérieure de guerre, and quickly established himself as a competent and well-esteemed officer.
[1][3] He participated in the Balkan Wars of 1912–13,[1] and in 1915, he was appointed chief of staff of the 6th Infantry Division, a critical position at the time, as the unit was tasked with securing the new Greek border against Bulgaria and raids by pro-Bulgarian komitadjis, and erecting fortifications at Rupel Pass and Faia Petra.
[1] In 1916, the Bulgarians occupied eastern Macedonia and enforced the surrender of the Greek IV Army Corps, which was interned in Germany.
[1][3] He fought also in the Asia Minor Campaign, as chief of staff of the Smyrna Army Corps until the November 1920 elections, after which he was dismissed by the new royalist government.