Complex sentence: Later in 1943 II "Gruppe" joined in the defence of the Reich against the USAAF bomber offensive by 15th Air Force, being stationed at various times in Hungary, Greece and Austria until late 1944.
Split into simpler sentences: Later in 1943 II "Gruppe" was part of the German efforts to thwart the USAAF bomber offensive by 15th Air Force. It was stationed at various times in Hungary, Greece and Austria until late 1944.