After retiring from politics he wrote the six-volume Byzantium in the 7th Century (Το Βυζάντιον στον Ζ' αιώνα, 1965–77), the first comprehensive study of the Byzantine state in that period.
In November 1922, his father was tried and executed by the military government as one of those principally responsible for the Greek defeat against Turkey in the so-called "Asia Minor Disaster".
The family was in dire financial situation, despite some help from his grandmother and Nikolaos Kalogeropoulos, forcing his mother to seek employment as a soprano singer as well as a dressmaker in various fashion designers.
[2][3][4] Among his initiatives during this tenure were the foundation of the unemployment fund, wage increases for night-shifts, holidays and Sundays, and the establishment of summer camps for children of low-income working families.
The fruit of his research would be the six-volume Byzantium in the 7th Century (Το Βυζάντιον στον Ζ' αιώνα, Estia 1965–77), later translated into French and English, for which he received the Prize of the Academy of Athens in 1970.