Original sentence: He was called to active duty in the Red Army that same year as the commander of an artillery platoon of 165th Howitzer Artillery Regiment, which took part in operations of the Soviet-Finnish Winter War
Edited sentence: He was called to active duty in the Red Army that same year as the commander of an artillery platoon of 165th Howitzer Artillery Regiment, which took part in operations of the [Soviet-Finnish Winter War when the Soviet Union invaded Finland