Born on 23 October 1861 at Levadeia, Ioannou entered the Hellenic Military Academy and was commissioned as a 2nd Lieutenant in the Engineers on 25 July 1884. In 1897, as a Captain, he participated in the Greek expeditionary force to Crete under Colonel Timoleon Vassos. By the time the First Balkan War broke out October 1912 he was a Lt. Colonel, and served as chief of staff of the Army of Epirus, under Lt. General Konstantinos Sapountzakis. Later, during the Battle of Bizani, he commanded a detachment of four Evzone battalions, and was distinguished for his drive and determination.