In October 1941 while a regimental commander in the 296th Infantry Division during Operation Barbarossa, the Axis invasion of the Soviet Union, he was a recipient of the Knight's Cross of the Iron Cross, the highest award in the military and paramilitary forces of Nazi Germany during World War II.

[2] World War II in Europe began on Friday 1 September 1939 when German forces invaded Poland.

During this invasion, Thoma commanded the 85th Infantry Regiment in its advance towards the Vistula, reported that thousands of Polish soldiers were captured.

[2] Although he regarded the population of the areas occupied by the advancing Wehrmacht as relatively primitive,[6] Thoma expressed sympathy for Ukrainians and Volga Germans that his unit encountered, noting their poverty.

48 in the Soviet Union, died on 30 October 1948 in a hospital at Shuya near Ivanovo, and buried in the camp cemetery.