Psaros first saw action in the Balkan Wars as a volunteer. He also took part in World War I, the Crimea expedition and the Greco-Turkish War (1919-1922) where, thanks to his bravery, his men were able to pass into Greece from Asia Minor without many casualties. Following that war, he furthered his studies in France and taught in the Greek Military Academy while rising to the rank of colonel.
Psaros took part in the 1935 Venizelist plot and attempted coup and, after its failure, was dismissed from the army. When Greece entered World War II, he sought re-appointment into the armed forces but was refused by the Ioannis Metaxas dictatorship.
Following the collapse of the front, during the German occupation, Psaros attempted to organise a resistance group in Amfissa with the help of Lt. Andreas Mitalas. Next, he went to Macedonia and organised armed groups there to fight the Bulgarians, who had followed the Germans into Greece, occupied much of northern Greece and had set their sights on permanent annexation.
Psaros returned to southern Greece and founded the resistance group EKKA (National and Social Liberation) along with politician Georgios Kartalis, officers Dimitrios Karachristos, Dimitrios Georgantas and others. The organisation's aims were to fight the Germans as long as the occupation lasted and, after liberation, work for social change. EKKA had followers and were active mainly in Central Greece but on Easter Monday, April 17, 1944, were attacked by the Communist forces of ELAS who sought to have a monopoly in the political future of Greece after liberation. Psaros was captured, shot, stabbed and killed. His body lay unburied for several days before it was interred at the local cemetery.