Complex sentence: The Admiralty went all out for the Hedgehog and before the end of 1941 it was being fitted into our escorts, later American escorts were similarly armed and by the end of the war the weapon had accounted for some fifty enemy submarines.
Split into simpler sentences: The Admiralty went all out for the Hedgehog and before the end of 1941 it was being fitted into our escorts. Later American escorts were similarly armed and by the end of the war the weapon had accounted for some fifty enemy submarines.