 On 14 August 1918 he was so seriously wounded in the left shoulder that he never flew in action again.The 28 victories he scored with Jasta 24 made up almost a third of its 90 claims; he and Friedrich Altemeier combined for over half the squadron wins.Despite being handicapped by the poorly built Pfalz, the Jasta under Kroll's leadership had suffered only 15 casualties.