Original sentence: On the British side of the battles in France, the advantages of the Sherman Firefly, were offset by the brute force frontal assault tactics of General Bernard Montgomery combined with a series of poorly coordinated air attacks on German positions,  during the three month long Battle of Caen in which over 400 British/Commonwealth tanks were lost before the British finally broke through
Edited sentence: During the three month long Battle of Caen, over 400 British/Commonwealth tanks were lost before the British finally broke through.On the British side of the battles in France, the advantages of the Sherman Firefly, were offset by the brute force frontal assault tactics of General Bernard Montgomery combined with a series of poorly coordinated air attacks on German positions