He was the third son of King Ludwig III of Bavaria and his wife Archduchess Maria Theresia of Austria-Este.

Infanterie-Regiments König, but shortly before the outbreak of World War I, he was given command of the 3. bayerische Infanteriebrigade, which was later renamed and became the 4.

Prince Franz led this brigade through its victories at Fort Douaumont, Passchendaele and Kemmelberg.

For his exemplary leadership during these operations he was awarded the Knight's Cross of the Military Order of Max Joseph on 25 May 1916 and on 28 October 1916 was given command of the entire 4.

Bayerische Infanterie-Division suffered severe loses during the Battle of the Somme and was transferred to Italian Front on border protection duties, where he stayed for the remainder of the war.