[2] In the First Balkan War of 1912–13 he served as a staff officer in the 4th Infantry Regiment and in the Metsovo Brigade in the Army of Epirus.

He participated in the Second Balkan War as a company commander in the 4th Regiment, and fought in the battles of Kilkis and Kresna Gorge.

His crowning moment was the victory at the Battle of Skra in May 1918, where he participated as chief of staff of the Archipelago Division.

In 1919 Protosyngelos participated in the unsuccessful Allied intervention in Ukraine, before going to serve in the staff of the Army of Asia Minor, where he was among the planners of the Greek summer offensive of 1920, which led to the capture of Prussa.

He served as Minister for Public Order in 1924, Inspector-General of Infantry (1926), Commander of the 2nd Infantry Division (1926–28) and of the Athens Garrison (1929), before becoming Director-General of the Ministry of Military Affairs (1930–34), Deputy Chief of the Hellenic Army General Staff (1934–35), and finally Commander of the Supreme War School (1935–36).