Kazimierz Fabrycy was born on March 3, 1888, in Odessa, in the Kherson Governorate of the Russian Empire.
Upon graduating from school in Niemirów he enrolled for a year-long military service in the Russian army.
He was the Viceminister of military affairs from 1926 to 1934, and commander of several infantry divisions during the interwar period in the Second Polish Republic.
During the Invasion of Poland of 1939, Fabrycy was the commander of Armia Karpaty and later the Romanian Bridgehead area.
After being evacuated to Romania, he was given assignments of small importance in the recreated Polish Army in the Middle East area.