Complex sentence: This meant that the 75 would use the same mounting as the 6 pounder; however, it was not until June 1944 that the Cromwell first saw action during Operation Overlord, the Allied invasion of Normandy.
Split into simpler sentences: This meant that the 75 would use the same mounting as the 6 pounder. In June 1944 the Cromwell first saw action during Operation Overlord, the Allied invasion of Normandy.