Hartlieb-Walsporn commanded the 5th Panzer Brigade in the early fall of 1939, then took charge of the 5th Panzer Division on 8 October 1939. As commander of this division, he participated in the Battle of France of 1940, but he came to be seen as a weak leader when the lightly defended French town of Le Quesnoy was able to resist his armoured forces for some four days. By May 28, he was in reserve; later in 1940, he was given command of the 179th Division, but in January 1942 he was again relegated to reserve or administrative posts and never again commanded front-line troops.