On 6 June 1944, Allied troops landed in the Operation Overlord during Hennecke’s command. Hennecke remained in Cherbourg-Octeville. The German commander-in-chief West, Gerd von Rundstedt, had foreseen that the city would be an important strategic target for the Allies because of its harbour, and ordered its destruction on 9 June. Hennecke, together with the city commander General-Major Robert Sattler and the harbour commander Kapitän zur See Witt, carried out the complete destruction of the port of Cherbourg, which began on 9 June during the Battle of Cherbourg and only ended immediately before the arrival of Allied troops in the port area on 25 June 1944. After the destruction of the harbour, further military resistance had become meaningless. Hennecke, the commander-in-chief, Lieutenant-General Karl-Wilhelm von Schlieben, and the remaining German defenders surrendered on 29 June to troops of the 9th US infantry division under Major-General Manton S. Eddy in Schlieben’s subterranean command bunker in St. Sauveur.
The destruction of the port of Cherbourg was regarded as exemplary by German and Allied observers as the most extensive destruction of a port facility. Hitler was so content with Hennecke’s performance that he awarded him the Knight’s Cross of the Iron Cross.
