Despite his responsibility, Potiorek remained in office. When the assassination and the succeeding July Crisis led to the outbreak of World War I, he became the commander of the Balkanstreitkräfte (Balkan Armed Forces). It is speculated that this "survivor's guilt" led Potiorek to take charge of the Austro-Hungarian army and lead the first mission to "punish" Serbia. He was reportedly very zealous in his actions (multiple times he claimed "I was spared at Sarajevo so that I may die avenging it!"), but was apparently an inept commander. The small Royal Serbian Army remained undefeated in all major battles and after the textbook military disasters at the Battle of Cer and the Battle of Kolubara with huge numbers of casualties, he was removed from command on 22 December 1914 and replaced by Archduke Eugen of Austria, a choice that reportedly made him suicidal.