Complex sentence: Later in the war, the "Luftwaffe" successfully trialed this method in May 1943, as the Japanese did entirely on "their" own from that same time onwards, with the Luftwaffe nicknaming this armament scheme the "Schräge Musik".
Split into simpler sentences: Later in the war, the "Luftwaffe" successfully trialled this method in May 1943, as did the Japanese. The Luftwaffe nicknaming this armament scheme the "Schräge Musik".