Tiger I tank ace Otto Carius commanded the second of three companies of "Jagdtigers" in "schwere-Panzerjäger Abteilung" 512. His postwar memoir "Tigers in the Mud" provides a rare combat history of the 10 "Jagdtigers" put under his command. He states that the "Jagdtigers" were not utilized to their full potential due to several factors, among them that Allied air supremacy made it difficult to maneuver around and the massive heavy gun needed to be re-calibrated from jarring after travelling off-road for even short distances. The vehicle was slow, having been equipped with the same engine as the already-underpowered Tiger I and Tiger II, and the vehicle's transmissions and differentials broke down easily because the whole 72-tonne vehicle needed to rotate for the gun's traverse. The enormous 128mm main-gun had to be locked down during the vehicle's maneuvers, otherwise its mounting-brackets would have worn out too much for accurate firing afterwards. As such, a crew-member had to exit the vehicle in combat and unlock the gun from its frontally mounted gun travel-lock before firing. According to Carius, in combat, he recorded that a 128 mm projectile went through all the walls of a house and destroyed an American tank behind it.