Michael Sionidis was born in the village of Grčište,[citation needed] Ottoman Empire (near Bogdanci in the present-day North Macedonia) in about 1870.

At the outbreak of the Macedonian Struggle in 1904, Sionidis fought against the pro-Bulgarian komitadjis,[b] acting in an area covering Grčište, Gevgelija and Doirani.

Sionidis first fought under Georgios Zira,[c] then under Emmanuel Katsigaris [bg],[d] before he finally founded his own militia.

[3] After the First Balkan War, Grčište came under Serbian control, and Sionidis moved to the village of Matsikovo (modern Evzonoi), which was at the time on the Greco-Serbian border.

Sionidis also participated in the Battle of Skra-di-Legen during World War I, and worked as a secret agent of the Third Army Corps behind enemy lines, in the area of Strumica.