Walcheren: Flooding an Island

The flooding of Walcheren was one of the most remarkable actions of the campaign to liberate northwest Europe in 1944, yet today it is one of the least remembered. Conducted to support two amphibious landings on the Dutch island, the flooding occurred against a background of worsening manpower shortages in Britain and Canada. Neither country was in a position to absorb heavy casualties by this stage of the war, yet the capture of Walcheren had the potential to be an extremely complex and costly operation.

Reference: Flooding Walcheren: Allied Conference of 29 September 1944

The reason for launching amphibious landings on Walcheren on 1 November 1944 can be summed up in one word - sustainability. The Allies had expected the campaign to liberate northwest Europe to involve a steady advance from Normandy towards Germany. In reality, they found themselves bottled up in Normandy for more than two months. Then at last came the breakout. The Germans suffered enormous losses during the retreat from Falaise in August and were unable to re-establish a defensive line. The Allies advanced into northern France and Belgium virtually unopposed. But a new problem quickly developed - logistics.

It was always clear that the availability of ports would be crucial to the progress of the Allies’ advance - hence the importance attached to the Mulberry harbour and the capture of Cherbourg soon after the D-Day landings. However, by early September, the Allied armies had reached Belgium and northeast France, and were still relying on a supply chain stretching back to Normandy. The logistical strain became increasingly severe. It had been hoped that the more northerly channel ports would soon fall into Allied hands, but the Germans strenuously defended Le Havre, Boulogne and Calais, compelling the Allies to lay siege to them, one after the other.

The capture of the channel ports was assigned to First Canadian Army, under General Harry Crerar, supported by Bomber Command and half of Coningham’s 2nd Tactical Air Force; the channel ports represented Bomber Command’s main effort in September 1944. They were ultimately captured, but their harbour facilities were largely wrecked by the action of German demolition teams.

In the meantime - indeed, before any of the channel ports had been liberated - British forces reached Antwerp, then the largest port in Europe. They encountered minimal opposition and, with the help of the Belgian resistance, captured the harbour virtually intact. Yet shipping can only reach Antwerp via an extended western approach through the Scheldt Estuary, and the land north and south of the estuary remained in German hands. To the north, the Dutch island of Walcheren dominated the mouth of the river. Walcheren was as strongly defended as any of the channel ports and was one of the most formidable parts of the Atlantic Wall: it was literally encased in concrete. To the south, the area around Breskens was also a German stronghold.

On 5 September, Eisenhower told Montgomery that it was vital to open up the approaches to Antwerp, but Montgomery did not embrace the task enthusiastically. His focus was to the northeast - to the Rhine and the German frontier - and he believed that Dempsey's Second Army might soon cross the Rhine and enter Germany if it was given logistical priority over the American forces further south. He did not secure the logistical support he was seeking but nevertheless persuaded Eisenhower that he should launch Operation Market Garden - the largest airborne operation of the war to date - in an attempt to establish a bridgehead across the Rhine. Market Garden proved a costly failure, but early in October, a month after the capture of Antwerp, Montgomery was still seeking a route into Germany. He had eventually to be forced, very reluctantly, to reorient his focus towards the Scheldt Estuary.

The task of capturing Walcheren was again assigned to the First Canadian Army. To begin with, it was necessary to secure the approaches to the island, namely the area around Breskens south of the estuary and the South Beveland Peninsula, east of Walcheren. This proved extremely difficult due primarily to the terrain, which favoured defence. It was largely polder-land, consisting of soft ground interspersed with numerous obstacles - drainage channels, rivers, streams and canals. The Germans had also flooded substantial areas. The few roads were narrow and often raised above the surrounding fields, so that vehicle and troop movements along them were extremely vulnerable. Ultimately, Breskens and South Beveland were taken, but their conquest proved difficult and costly, and it seemed certain that Walcheren would be an even more hazardous objective.

We will consider Walcheren’s defences in more detail later. For the moment, the key point is this: to stand any chance of capturing the island without incurring heavy casualties, it was vital for the Allies to identify and exploit German vulnerabilities. They came to the conclusion that there were two.

First, while the Germans occupied very strong defensive positions on land, the Allies had air superiority and complete control of the sea. Hence, there was clear scope for exploiting all three environments to gain advantage over the German defenders, exposing them to multiple parallel air, land and maritime effects. Ultimately, this would involve an extended preparatory air bombardment of the island, one ground assault from the South Beveland Peninsula (which failed), and two amphibious landings, which were both staged successfully on the morning of 1 November. The first of these, Operation Infatuate 1 (155 Brigade spearheaded by 4 Commando), took place at Vlissingen; the second, Infatuate 2 (4 Special Service Brigade), was staged at Westkapelle on the west coast of Walcheren. Extensive fire support plans were drawn up, incorporating air support, long-range artillery fire from across the Scheldt, and naval bombardment for the operation at Westkapelle.

The second German vulnerability lay in the topography of Walcheren: much of the island was below sea level. Crerar’s principal corps commander, Lieutenant General Guy Simonds, therefore proposed bombing the sea wall and using flooding as an offensive weapon. Simonds’ proposal could be seen as an early application of ‘effects-based’ warfare. Obviously, he had no interest in destroying the sea wall per se. Rather, he was interested in the effects of the subsequent flooding, which he expected to eliminate German defences behind the sea wall and destroy the integrity of the defending force - its command and control, movement and logistics. The German garrison would be left fragmented and confined to the few higher areas of Walcheren.

Crerar 

Simonds

Flooding was also likely to strike a significant blow against German morale. Germany was scraping the barrel for manpower by the later months of 1944 and the quality of some of the defending troops on Walcheren was very questionable. Finally, the coast around Walcheren was (and still is) almost entirely characterised by high sand dunes or man-made sea walls. There were very few locations where a large amphibious force equipped with tanks and support vehicles could have exited the island's beaches in the absence of a physical breach in the sea defences.

Simonds’ proposal was received with considerable scepticism. With the obvious exception of the dams raid (a very different type of operation), bombing had never been used in this way before; the sea wall appeared to be a formidable target, measuring 70 metres at its base, and 20 at its apex. Another obvious objection to flooding was that it might impose handicaps on the amphibious assault force that were no less severe than those inflicted on Walcheren's German garrison.

Nevertheless, he was not dissuaded. Already famed for his exploitation of 'Kangaroo' armoured personnel carriers in Normandy, by the later months of 1944 he had another card up his sleeve - tracked amphibians like the Buffalo and the Weasel. Potentially, these would allow his forces to manoeuvre across flooded areas inaccessible to their adversaries.

A Buffalo landing from the Scheldt Estuary

A Weasel in Vlissingen, November 1944

Events subsequently played into Simonds' hands. First, on the night of 23/24 September, the RAF attacked and emptied a significant section of the Dortmund-Ems Canal. The canal was a banked up structure quite similar to parts of Walcheren's sea wall; consequently, there was now a rough precedent for the sort of operation that Simonds had in mind. Second, a few days later, General Crerar fell seriously ill and Simonds was placed in temporary command of First Canadian Army. In this new capacity, he was perfectly placed to promote his plan and managed to secure the support of both Eisenhower and Montgomery. The RAF subsequently agreed to mount an experimental attack on 3 October near Westkapelle (one of the most exposed sections of the sea wall).

Inevitably, the flooding threatened to cause severe collateral damage, extending from civilian casualties to the inundation of buildings and agricultural land, loss of livestock and deterioration of soil quality. The Dutch were allies, and their government-in-exile had been based in Britain since 1940. They were not consulted about the plan, but they were advised of its basic intent.

The response - a predictably strong protest - was passed to SHAEF but rejected. However, the Allies did agree to broadcast warnings to the inhabitants of Walcheren and to drop leaflets. The Dutch were told that the bombing of German forces in coastal areas was imminent and that flooding was likely. People were advised to leave these areas if possible, or to move to places of safety well away from German troops. Unfortunately the full significance of these warnings was not widely appreciated and, in any case, there were very few obvious refuges.

On 3 October, 259 Lancasters and Mosquitoes of Bomber Command delivered 1,262 tons of explosive on the sea wall at Westkapelle. The wall was breached, and the flooding of Walcheren began. This first attack was followed on 7 October by two more on either side of Vlissingen. A fourth raid took place on the 11th near Veere, to the north of the island. The success of the flooding lent impetus to the plans for amphibious landings. In the meantime, the German perimeter defences on Walcheren’s sea wall were repeatedly targeted by Allied air attacks.

Westkapelle, 3 October 1944

Bombs falling on the sea wall west of Vlissingen,
7 October

East of Vlissingen, 7 October; note the German anti-
aircraft artillery positions about to be inundated 

Veere under attack, 11 October 1944

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Depth is critically important to the strength of a prepared defensive position; a single line of defences may be pierced with relative ease. On Walcheren, the Germans had achieved depth through the construction of an elaborate interior defensive system, part of which is shown in the photographs below. The gun emplacements here were actually designed to defend Vlissingen from an inland flanking attack if the Allies landed on Walcheren's northern coast. The nearby waterway was in fact a specially constructed anti-tank ditch.

Air reconnaissance photo of Vlissengen's interior
defences

The same defence line today

Two more gun emplacements next to the anti-tank ditch

A few fields away, the Germans positioned a coastal gun battery named W10 by the Allies - all the main German positions here were assigned ‘W’ numbers. Typically, the batteries housed two or more large guns ranging from 100 to 155mm calibre. Some, like W10, pointed north; others pointed south-west to protect the Scheldt Estuary. Positioned inland, the larger gun batteries were less vulnerable to naval gunfire than those on Walcheren's perimeter; only the fire control post would have been sited directly on the coast.

Virtually all of Walcheren’s perimeter fortifications have now gone, but the surviving interior defences give some idea of how formidable the island fortress was in 1944. There were approximately 20 large (75mm to a maximum of 220mm) batteries on the sea wall, with up to six guns each; a further ten batteries were positioned inland. Most were housed in closed casemates by late 1944, although a few were still in open emplacements.

The W10 battery

The W10 battery flooded in 1944

W12

An observation bunker on the coast that served one of
the inland gun batteries; the bunker interior has been
perfectly restored

The larger batteries made up only part of the defensive system. There were many more lighter gun positions, pillboxes and strongpoints, supported by networks of trenches. Minefields, barbed wire and beach obstacles were liberally employed. Vlissingen was almost a fortress in its own right. Elsewhere there were two basic lines of defence – the coastal defences on the sea wall and a second line in the hinterland. The second line effectively blocked all the exits from the west coast - from Westkapelle, Zouteland, Domburg, Dishoek, and Vlissingen itself. The whole system was planned with immense thought, care and expertise, and many defensive positions were designed and sited to be mutually supporting.

Before September 1944, the garrison on Walcheren numbered around 4,000, largely elements of the 70th Division. They were a mixture of low-quality garrison troops and more experienced troops who had picked up stomach wounds and complaints in earlier campaigns, and therefore had special dietary requirements (hence their nick-name of the ‘white-bread’ division). However, during September and October, their numbers were swelled by elements withdrawn from Belgium, Breskens and South Beveland, so that by mid-October an estimated 9,000 Germans were on Walcheren. Yet many (although by no means all) were exhausted, demoralised and unwilling to offer more than token resistance. The larger coastal batteries were manned by German naval marines.

The German high command had assigned top priority to the defence of the channel ports and the Scheldt Estuary after the Allied breakout from Normandy and the fall of Antwerp. It was clear that logistics were the Allies’ Achilles heel and would determine the pace of their advance towards Germany. Hitler himself issued an explicit directive ordering that ‘fortress Walcheren’ had to be held at all costs. ‘Fortress’ status indicated that German military personnel on the island would be subject to particularly severe disciplinary measures.

By October 1944, the Germans were expecting the Allies to attack Walcheren, but they do not appear to have anticipated the destruction of the sea wall and the subsequent flooding. In some ways this is surprising, as they had often themselves used flooding to enhance defences around areas such as Normandy, Dieppe, Breskens and South Beveland. The first flooding operation (3 October) was executed by a force of 250 Lancasters, accompanied by nine Mosquitos used for target marking. The raid was timed to occur at high tide, when the wall would be under greatest pressure from the sea.

The Lancasters were to arrive in nine waves. The first eight would carry a mix of 1,000lb and 4,000lb bombs, including delayed-action bombs to prevent the Germans from repairing the sea wall. For accuracy, they were to attack from an altitude of between 7,000 and 9,000ft. They would approach Walcheren from the north-west, release their weapons, and then turn immediately away from the island to limit their exposure to German anti-aircraft fire. The ninth wave would consist entirely of 617 Squadron aircraft, carrying Tallboys and, of necessity, bombing from higher altitude. The Special Instructions contained in the Operation Order read: ‘By this means it is hoped to achieve a concentration of craters sufficient, in conjunction with the scouring action of the spring high water, to breach the sea wall.’ ‘Hoped’ is the key word here: no one had any idea whether the plan would actually work.

Surprisingly, Bomber Command’s task proved less difficult than expected. The attack began at 1300 and the wall was breached at about 1400 by the fifth wave of Lancasters. By the time 617 Squadron reached Walcheren, the sea water was pouring into the island interior, so they returned to base with their Tallboys. Yet although Bomber Command had quite easily punctured the wall, it soon became clear that the flooding process would be very protracted unless further attacks were launched - hence the follow-up raids at Vlissingen and Veere. The later missions all involved fewer aircraft than the Westkapelle operation, and no more 4,000lb bombs or Tallboys were employed. Throughout, the Luftwaffe was completely absent; the only significant problems were caused by cloud in the target areas, which forced aircraft to descend to lower altitudes where the threat from AAA was greater (the ‘hard deck’ was 4,000ft). But there were very few losses.

The flood water eventually covered three quarters of Walcheren’s surface area. Only the perimeter, Middleburg, parts of Vlissingen and the extreme east of the island were not inundated.

The flooding achieved precisely those effects that Simonds had anticipated. Most obviously, it completely destroyed the German second-line defences. The inland batteries and pillboxes were rendered useless and the vast majority never fired a shot in anger. Trenches were obliterated; weapons and ammunition were damaged or lost completely. Hence, across much of the island, the German defences were confined to a single perimeter line; there was no longer any scope for defending in depth.

Of particular note, flooding eliminated any threat from the inland batteries covering the Westkapelle area - the target for Operation Infatuate 2. Consequently, on the morning of 1 November, the only German batteries defending Westkapelle were located in isolated positions along the coast. They nevertheless engaged the landing force very effectively, causing heavy losses to the Royal Navy's Support Squadron, damaging a number of landing craft, and placing the entire venture in jeopardy for a time. Had the inland batteries been active too, Infatuate 2 would probably have failed.

Additionally, by neutralising the W10 and W14 batteries, and several others, the flooding operation substantially reduced the volume of fire that the Germans could direct towards the mouth of the Scheldt - the location of Infatuate 1. Flooding provided a far more effective means of suppressing the German defences than direct targeting from the air or naval bombardment.

The W14 battery at Westkapelle before
and after the raid of 3 October 1944

One of the W14 casemates today

Secondly, the flooding caused the German garrison to disintegrate. Large numbers of troops were moved away from the western coast (where the Allies were planning to land), to dry ground on the east of the island. Centralised command and control became impossible and the senior German commanders found themselves cut off in Middelburg, with their troops dispersed and isolated around the island. Movement, re-supply and reinforcement could only be effected with enormous difficulty, if at all. One of the three main batteries covering Westkapelle, W13, ran out of ammunition during the Allied landings because flooding had rendered re-supply impossible.

The W13 battery, south of Westkapelle

A superb oblique shot of W13's four casemates

Thirdly, German sources suggest that there was a severe decline in their morale - another important Allied objective. This is easy to understand. The German forces on Walcheren were already cut off from the mainland, exposed to constant air attacks, and threatened with invasion. Now they were flooded out and cut off from their commanding officers and such supplies as had been accumulated on the island for its defence. Half-hearted efforts to build an emergency sea wall to stem the flooding proved fruitless, for the Germans lacked sufficient manpower, materials and technical expertise. 

Fourth, the breach in the sea wall at Westkapelle was effectively incorporated in the Allied landing plan. On 1 November, a significant proportion of the amphibious force went straight through the gap and then fanned out behind the German defences. No such manoeuvre would have been possible while the sea wall remained intact.

The landing beaches at Westkapelle

Buffaloes advancing through the Westkapelle gap

In summary, Bomber Command’s action in breaching Walcheren’s sea wall played a crucial part in the ultimate success of Operation Infatuate 1 and 2. The flooding significantly reduced the capability of the German defences, caused the disintegration of the island garrison, and weakened the defenders’ morale; the Westkapelle gap also provided the Allied landing force with a vital route off the beach. It was an inspired concept on the part of Lieutenant General Simonds’ in terms of thinking ‘outside the box’, thinking about the effects of military actions (and not just the attrition of the enemy), and identifying - as well as exploiting - key German vulnerabilities.

Collateral damage across the island was immense. Although the vast majority of civilians survived, 160 died at Westkapelle out of a population of 2,300. Located adjacent to the sea wall destroyed by Bomber Command on 3 October, the town was particularly vulnerable. Elsewhere, there was widespread and severe damage to residential property and the local economy. Soil was contaminated by salt water, and thousands of cattle were drowned. And although work to rebuild the sea wall began in the spring of 1945, the last gap was not finally closed until February 1946.

However, in the longer term, the flooding would paradoxically have beneficial economic effects, for it provided an opportunity in the post-war years for the island’s agricultural system to be completely overhauled. The historic and heavily subdivided field layout, with its multiplicity of minor waterways, was replaced by a far more modern system based on larger fields and more modern drainage provisions. This allowed improved farming techniques to be introduced, and agricultural productivity rose significantly as a result. By the mid-1950s, agricultural output on Walcheren vastly exceeded the levels recorded before the Second World War.

Beyond this, the collateral effects of the flooding must be considered in context. Walcheren was of enormous strategic importance to the Allied war effort in north-west Europe; moreover, the island’s defences had the capacity to inflict very heavy casualties on Allied landing forces. Hence, although the cost in terms of collateral damage was high, the flooding of Walcheren unquestionably saved the lives of many Allied troops. Allied casualties during the landings numbered 818 killed, wounded and missing, while the total for the capture of the island, including the landing phase, did not exceed 1,500.

Furthermore, a more protracted conventional battle for Walcheren - involving higher Allied casualties - might also have had calamitous consequences for the island's population and economy. It is worth remembering that barely a single building in Vlissingen was left intact by the fighting in November 1944, but much of the damage was inflicted by Allied artillery fire from across the Scheldt Estuary, or by the street-to-street, house-to-house clearance that was required to evict the Germans.