Operation Undergo

Operation Undergo (Siege of Calais)
Part of Western Front of the Second World War
A British soldier poses next to the recently captured German 380 mm gun Todt Battery at Cap Gris Nez.
Date 22 September – 1 October 1944 Location Calais, France 50°57′22.12″N 1°50′28.90″E / 50.9561444°N 1.8413611°E / 50.9561444; 1.8413611 Result Allied victory
Belligerents
Canada  United Kingdom	Germany
Commanders and leaders
Daniel Spry	Ludwig Schroeder
Strength
unknown	7,500 Calais
Casualties and losses
260 killed or wounded German shelling of Dover: 5 military personnel[1] 16 civilians[2]	9,128 captured incl. 1,600 from Cap Gris Nez
Calais class=notpageimage| Calais in Northern France, a sub-prefecture of the department of Pas-de-Calais

Operation Undergo was an attack by the 3rd Canadian Infantry Division on the German garrison and fortifications of the French port of Calais, during September 1944. A subsidiary operation was executed to capture German long-range, heavy artillery at Cap Gris Nez, which threatened the sea approaches to Boulogne. The operation was part of the Clearing the Channel Coast undertaken by the First Canadian Army, following the success of Operation Overlord and the break-out from Normandy. The assault on Calais used the tactics of Operation Wellhit at Boulogne, sealing the town, bombardments from land, sea and air, followed by infantry assaults supported by armour, including flame-throwing tanks and creeping barrages.

The city had been declared a fortress (Festung) but when pressed, its second-rate garrison needed little persuasion to surrender. This reluctance to fight to the end was repeated at Cap Gris Nez. The 7th and 8th Canadian Infantry Brigades started the main attack from south-west of Calais and cleared the outer defences on the southern and western sides of the port. The 8th Canadian Brigade was then transferred to the eastern side and the inner defensive lines were attacked from both sides. The Germans called for a truce which, after some misunderstanding, led to an unconditional surrender of the garrison. The 9th Brigade took the heavy batteries on Cap Gris Nez at the same time.