Heeresgruppe E
After the Yugoslav Partisans and the Red Army expelled the Germans from Belgrade in the Belgrade Offensive, the retreating Wehrmacht and the Croatian Armed Forces used fortifications to protect the withdrawal of German Army Group E from the Balkans. With help from their Soviet allies, the Partisans (by then recognized as the Yugoslav army), joined by Bulgarian and Italian forces, fought a difficult winter campaign and finally broke through the front on 12 April 1945.