[1] Upon the outbreak of World War II, Bäßler was serving as Chief of Staff of XI Army Corps and participated in the Invasion of Poland in this capacity.

He remained on the staff of XI Corps through the Battle of France, the Invasion of Yugoslavia, and Operation Barbarossa, the latter as part of Army Group South, until February 1942.

[1] In April 1942, and now a generalmajor,[Note 1] he was given command of 9th Panzer Division[3] which was then operating on the Eastern Front, around the town of Shchtschigry, to the east of Kursk.

In October 1943, the division, intended to be a static unit with little organic transport, was moved to the south of France and the following February, Bäßler was promoted to generalleutnant.

[Note 2] The day after the launch of Operation Dragoon, the Allied invasion of Southern France in mid-August 1944, Bäßler and his division were ordered to hold the city of Toulon.