Complex sentence: Mertens transferred to Jagdgeschwader 3 flying with their 9 Staffel (squadron) in the Battle of Britain as his unit provided escort cover for German bombers attacking England and on 26 October 1940 he shot down another Hurricane fighter.
Split into simpler sentences: Mertens transferred to Jagdgeschwader 3 flying with their 9 Staffel (squadron) in the Battle of Britain. His unit provided escort cover for German bombers attacking England and on 26 October 1940, he shot down another Hurricane fighter.