Heeresgruppe E
From September 1944 to January 1945, Army Group E pushed its way through Macedonia, Kosovo, Sanjak, and Bosnia, and soon their sole available escape route was in a line between Sarajevo and Slavonski Brod. For this reason, it was of vital significance for the Germans to defend the zone around Slavonski Brod, which was threatened by the Soviet-Yugoslav advance through Syrmia. To prevent Army Group E from being cut off, the German South-East command prepared seven successive fortified defense lines between the Danube and Sava river from Ruma to Vinkovci. The Syrmian Front campaign consisted of Yugoslavian attempts to break through these lines of defense.