Complex sentence: The records of Schwere Panzer Abteilungen (Heavy Tank Battalion) 501 which state that the commanding officer was killed and had lost so many tanks at Hunt's Gap that it ceased to be an effective fighting force.
Split into simpler sentences: The records of Schwere Panzer Abteilungen (Heavy Tank Battalion) 501 which state that the commanding officer was killed. In addition they had lost so many tanks at Hunt's Gap that it ceased to be an effective fighting force.