Ever since the Anglo-Canadian raid on Dieppe in August 1942, the Germans had been convinced that the Allies would try to capture a port during their next landing attempt, in order to ensure the swift arrival of the men, equipment and supplies they would need.
Accordingly, all the major ports along Europe’s western coastline were turned into veritable fortresses (Festungen), bristling with large-calibre guns intended to repulse any invasion fleet. The Seine bay sector was thus framed by the two fortresses of Cherbourg and Le Havre.
The Cherbourg Fortress, commanded by General Karl von Schlieben, extended along a 30-kilometre stretch of sea front on either side of the city, from Jardeheu in the west to Cape Lévi in the east. There were no fewer than a dozen heavy batteries here, with a total of more than forty guns of a calibre ranging from 105 to 240 mm. The city and port were dotted with numerous blockhouses, antitank walls and anti-aircraft artillery positions.
Inland, the fortress was protected by an outer defensive ring, forming a curve twelve kilometres long, and an inner ring on the very outskirts of the city. Constructed in considerable haste, these defences were the weakest part of the system. When the American troops who had landed at Utah Beach launched an attack at the end of June 1944, they soon smashed through these inland defences. The Allied fleet, however, which had started bombarding Cherbourg during the attack, was kept at bay by the heavy coastal batteries.