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Clearing the Channel Ports
Operation Undergo -
The Capture of Calais & Cap Gris Nez

Jan Hyrman
The assault itself went on in much the same way as before at Le Havre or Boulogne, with the 79th Armoured Division making gaps in the defences, while the 7th and 8th Canadian Infantry Brigades followed on foot. By noon the next day, the Sangatte battery had already been captured along with the battery commander and 280 of his men. In the evening of 26th September, the Canadians have already captured 28 officers and 1,525 other ranks. The early capture of Sangatte effectively cut the perimeter in half, causing the two flanks to become separate thrusts rather than a united offensive.

The city iself on the right flank to the east of Sangatte proved the toughest nut to crack. Heavily defended and fortified enemy outposts based on old ports within the city were frequently
The Calais area was the centre of the Atlantic Wall, from which the flanks of the line of fortifications stretched hundreds of kilometres to both north and south, from the Pyrenees to the Arctic Circle. Here, Adolf Hitler awaited the Allied invasion until well into August 1944, when the Allies were already firmly established on the continental soil and any effective counter-attack, which would "drive them into the sea" was absolutely out of question.

It was the only point from where the British ports of Dover and Folkestone could be shelled by German cross-channel guns and where the invasion of Fortress Europe would be most likely due to the vicinity of Britain.

The defences here were the most formidable, the guns emplaced in the reinforced concrete and steel emplacements would be the largest available, the counter-invasion measures would be as near completion as possibly imaginable. Yet most of these defences were prepared to counter an invasion from the sea and the landward side was not left largely undefended only by the care of the local German commanders, as Hitler was still looking out to the sea.

Five points were to be engaged during Operation Undergo. The first was the area around Cap Gris Nez. Four 380mm guns were placed here, forming Batterie Todt, parts of which are still preserved and serve as a part of the Atlantic Wall Museum at Audinghen at Cap Gris Nez. The Floringzelle and Framzelle area was the location of the Batterie Groesser Kurfuerst, a battery of four 280mm guns with an all-round traverse. The Batterie Gris Nez had further three 170mm guns, while Batterie Wissant further to the east had other guns of 150mm calibre, all pointed seaward. Another strong outpost was near Sangatte, where 406mm guns of the Batterie Lindemann were emplaced in concrete bunkers with walls 3.6 (12') to 4.9m (16') thick. Other outposts were at Escalles off Cap Blanc Nez.

All these had heavy anti-aircraft defences consisting of the 88mm and 20mm guns, most of which were to be converted for the defence of the perimeter of Calais and Cap Gris Nez. The cross-channel gun emplacements were not entirely devoid of landward defences, though. Anti-tank ditches, some of them concealed, minefields, wire, concrete pillboxes, all of these were available to the defenders, however, they lacked a conception. Their garrison of marine troops was also a strong factor, which strongly influenced the efficiency of these defences when the Allies began encircling the area.

Together with Dunkirk, Cap Gris Nez and Calais formed a belt of furious activity throughout the German occupation. Huge concrete installations from which the infamous V-1 and V-2 rockets where fired were located at d'Eperlecques and Saint-Omer south of Dunkirk, while the area around the small village of Mimoyecques hosted the experimental underground site, where the V-3 cross-channel rocket-assisted gun was to be built.

The wide range of targets, the delay in getting to Antwerp caused by reducing them by force and the estimated cost were also causes of Montgomery's early decision to encircle Calais and Dunkirk and to leave these two locations contained for the rest of the war. However, after the capture of the port of Boulogne, the Royal Navy expressed concerns about shelling of the Channel traffic by the coastal batteries in the area, which could deny the Allies the free use of Boulogne.

By noon on 5th September 1944, elements of the 7th Canadian Reconnaissance Regiment and the 3rd Canadian Infantry Division succeeded in containing the garrisons of the area, the 7th Canadian Infantry Brigade arrived later from Boulogne to assist with the encirclement and containment. Gathering of intelligence data started immediately, sourcing information from interrogations of prisoners of war and local civilians. One of the locals actually brought a complete map of the defences around Sangatte, among other papers "the Germans had left behind". 

The German line of defences, where the Canadian advance was stopped or diverted, was based on flooded low ground as no high features similar to those around Boulogne were in the vicinity. Defenders were also aided by natural features such as canals or dykes (the city was built on a series of islands), strongly defended or covered by artillery or small arms fire from pre-planned outposts.

Oberstleutnant Ludwig Schroeder was later found to be in command of the garrison, but after his capture, his interrogators reported that he was found to be a "mediocre and accidental" leader, who was charged with commanding the area only because he happened to be around. Oberstleutnant Schroeder had been in the Calais area since 30th August 1944, when Hitler was only starting to realize the invasion for which he was waiting had already taken place at Normandy nearly three months earlier.

First attempts to close in on the defences was made on 12th and 13th September 1944, but were opposed by furious artillery shelling, the Allied demand for surrender rejected.

Despite plans to begin the assault earlier, it was not possible due to various reasons, including the prolonged siege of Boulogne, to commence operations around Calais before 25th September 1944. For days, the German garrison was being pounded by Allied shelling by strong artillery formations, which had been brought over after the completion of Operation Wellhit. These units had to be brought in under a huge smoke screen to block them from view of the German observers. This smoke screen lasted for six days, pausing only for air bombardment, using up 147 tons of smoke generators.
encountered and had to be reduced with the assistance of rocket-firing Typhoons and flame-throwing Crocodile tanks. Crossing the canals of Calais proved to be a formidable task and once they had been crossed, troops could be easily cut-off. This danger materialized for two companies of the 1st Battalion Canadian Scottish Regiment, who managed to cross the canal in the western part of the city, but were cut off, without food and low on battery power for their radios.

Due to a large number of civilians caught up in the city and subjected to air and artillery bombardment, a truce was arranged in the morning of 29th September 1944 for their evacuation. This brought rather peculiar problems. The civil population was brought out of the perimeter using both Allied and German trucks, the German truck drivers often refusing to go back and insisting on being taken prisoner (including Schroeder's personal driver). Despite some initial concerns that accepting their requests could constitute a breach in the conditions of the truce, the Allies obliged.

While the truce was still in effect, another meeting of Allied and German officers took place, creating some confusion as the German garrison commander offered to surrender two hours after the truce was supposed to end. This was rejected off-hand by the Canadians, but the Germans obviously understood from their superior that they were expected to lay down arms, while the Canadians commenced artillery fire as soon as the truce ended.

Following this misunderstanding, the official German surrender was accepted from Schroeder's hands in the evening of 30th September 1944.

The capture of Cap Gris Nez became an essentially separate operation, not affected by the truce or the ensuing confusion about the German surrender in the city.

The assault assisted by Crocodiles, flail tanks and A.V's.R.E. was to be mounted following the artillery preparation by one field regiment, two medium regiments and two heavy artillery batteries. More than 1,000 rounds were expected to be fired during the operation, Air Observation Posts were, as before, available to direct fire. A unique form of artillery support was prepared by the battery in the St Margaret's Bay in Kent, whose railway guns fired 68 rounds and managed to damage all four guns of the Batterie Gris Nez to varying extent. The Bomber Command contributed by dropping more than 3,500 High Explosive (H.E.) bombs, together with rockets launched at tactical targets by Typhoons.

When the assault started, considerable number of specialized armoured vehicles were lost to mines or got hopelessly bogged down in craters created by the air bombardment. Only a single flail tank got far enough to force a gap in the minefields for the infantry. Soon after the defences were breached, the cross-channel gun emplacements surrendered.

The Canadians lost 3 officers and 39 men, out of whom 5 were killed, while the Germans lost 26 officers and 1,500 other ranks captured. The German garrison was found to know very little of what was going on outside of their bunkers.