During the German occupation in 1918, he organized the underground Estonian Defence League.

He commanded in the biggest armoured conflict of war that resulted in the capture of Pskov.

[clarification needed] After the war, Parts served as commander of the Armoured Trains Brigade from 1921 to 1923, and later as inspector.

In 1940, Soviet occupation authorities arrested Parts, and he was shot in imprisonment the year after.

Six weeks before his death, a Soviet destruction battalions doused his son Emil-Mauritius (1912–1941) with acid and killed him.