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Zeebrugge 1918

The Great War’s Greatest Raid

In 1917, Britain was in danger of defeat. Germany’s U-boats (submarines) were choking seaborne commerce. In April 1917 alone, 169 British merchant ships were sunk, as were a quarter of all merchant ships sailing from British ports that month, and outrage at Germany’s unrestricted submarine warfare caused the United States to enter what was then called the Great War. But it would be months before the U.S. Army and Marine Corps could be in action in France and Belgium. Britain had to overcome the U-boats.

This was a slow and costly battle, using merchant ship convoys, more capable aircraft and warships – British and American – and new technology weapons (such as the depth charge) and sensors (the hydrophone, the original passive sonar). The most potentially decisive anti U-boat approach was “attack at source”: striking at the U-boat bases, which were heavily defended with minefields, coast artillery batteries, antiaircraft guns, and reinforced concrete submarine pens.



A contemporary sketch map of the Zeebrugge raid, April 23, 1918, showing the locations of the mole, the canal exit, and the locations of the British warships and blockships involved. The Times of London


The main U-boat bases in Germany were beyond striking range. Those at Zeebrugge and Ostend in German-occupied Belgium appeared to be potential targets. U-boats, shuttling between the ports using Belgium’s inland canals, penetrated British minefields that protected the cross-Channel lines of communication 30 times a month. German destroyers and torpedo boats based there were in position to raid British shipping.

These bases were to have been the target of a British infantry division making an amphibious landing on the Belgian coast, in support of the 1917 summer offensive. But the British, reluctant to carry out a major amphibious operation after being defeated by the Turks at Gallipoli in 1915, cancelled the operation. Instead, Royal Navy monitors bombarded the two bases. British aircraft attacked them. The U.S. Navy, a supporter of “attack at source,” organized a Marine Corps air wing to join these attacks, but it would take months to become operational.

Planning the Raid

In January 1918, Royal Navy Vice Adm. Roger Keyes took command at Dover. An aggressive commander, even though he lacked familiarity with special operations or the Belgian coast, his plan was to “strike at the root of the evil by attempting to block the sea-exits” at the two bases, sinking obsolete concrete-filled warships with skeleton crews and a few guns – blockships – in the channels and sealing the U-boats and destroyers in harbor. To prevent German coast defenses from sinking the blockships as they approached at Zeebrugge, the modified obsolete cruiser HMS Vindictive would carry the 4th Battalion Royal Marines and sailors to launch an amphibious assault against coast artillery positions on the mole, a mile-long projecting sea wall around the entrance to the harbor and canal, connected to the mainland by a viaduct, which would have to be destroyed to prevent German reinforcements reaching the battle. Keyes’ plan relied heavily on extensive smokescreens to block German coastal guns from sinking either the blockships or the mole assault force.



The raiding force included volunteers from the British Grand Fleet and the 4th Battalion, Royal Marines Light Infantry. These are the Royal Marines and sailors from just one dreadnought that volunteered for an unspecified hazardous mission that proved to be the Zeebrugge-Ostend raids. National Archives


Keyes wrote that he “was given an absolutely free hand, not only to make my own plans for the blocking of Zeebrugge and Ostend, but to select all the people who carried them out.” Keyes’ complex plans were hastily drawn up and had many potential points of operational failure. Intelligence to support the planning was limited, in part because of the need for strict operational security.



The Royal Navy of 1918 had no preexisting special operations forces. Both the amphibious assault force and ships’ crews were volunteers. Selected fleet-wide for an undisclosed hazardous mission, they included Canadians, Australians, and New Zealanders. Each part of the raiding force trained and rehearsed separately, starting in January 1918.

Keyes planned two complex, simultaneous direct attacks involving some 150 vessels, including escorts. Two heavily armored monitors with 15-inch guns, HMS Erebus and Terror, would provide naval gunfire support. Coastal motorboats – predecessors of the World War II motor torpedo boats – and motor launches would attack defenses, rescue blockship crews, and put down smokescreens. The force was ready at the end of March. British forces were hard pressed on the battlefields of the Western Front by the German spring offensives. There was a great need for a dramatic operation to boost morale.



Two Royal Navy motor launches alongside the battle-scarred mole at Zeebrugge after the armistice. Motor launches, many with Canadian crews, played a major role in the raids. Author’s collection


On April 11, wind, weather, moon, and tide conditions all favorable, the force set sail, under conditions of wireless silence, for the Belgian coast. Strong fighter escort prevented German air reconnaissance. Keyes was in command, aboard the destroyer HMS Warwick. When the wind shifted unexpectedly, making the all-important smokescreens impossible, Keyes felt he had no choice but to send a recall signal.

The force sailed again on April 13. Unfavorable winds, soon after leaving port, again forced a recall. Keyes was afraid that the aborted raids had alerted the Germans (they had). He could not keep the force in readiness until the next month’s moonless nights. He requested permission to attack as soon as winds and tides permitted, even in bright moonlight.

The Raid Goes In

The force sailed for the third time on the evening of April 22. By midnight, the wind still stood fair. The raid would take place on April 23, St. George’s Day, the patron saint of England. Keyes signaled the force by shrouded blinker light, “St. George for England.” Capt. Alfred Carpenter, commanding Vindictive, signaled back, “May we give the dragon’s tail a damned good twist.”

This time, the coastal motorboats were able to put down their thick smokescreen. This and the engine noise – the Germans had sophisticated sound detection equipment – alerted the defenses, already at high readiness. German coast artillery was locked and loaded when, just before midnight, Vindictive emerged from the smokescreen 200 yards from the most heavily defended section of the mole.



Iris (right) and Daffodil, the two ferryboats that went alongside the mole in support of Vindictive. They somehow survived the intense German fire. Author’s collection


Carpenter wrote, “the noise was terrific and the flashes of the mole guns seemed to be within arm’s length. Of course it was, to all intents and purposes, impossible for the mole guns to miss their target. They literally poured projectiles into us. In about five minutes we had reached the mole, but not before the ship had suffered a great amount of damage to both material and personnel.”

Vindictive’s surviving Marines and sailors were supposed to surge up gangways and ramps onto the mole and take the German gun positions. These had been shot to pieces by machine-gun fire from concrete emplacements. Most of the gunners aboard Vindictive were already casualties. Those that remained shot it out with the German guns. This gave Royal Marine Sgt. Harry Wright and his comrades of the assault force a chance. “Up the ramp we dashed, carrying our ladders and ropes, passing our dead and wounded lying everywhere and the big gaps made in the ship’s decks by shellfire. Finally we crossed the two remaining gangways, which were only just hanging together, and jumped onto the concrete wall, only to find it swept by machine-gun fire. Our casualties were so great before the landing that of a platoon of 45 men only 12 landed.”

Vindictive had landed against the mole 300 yards – all swept by machine guns and offering little cover – farther away from the coastal guns than planned. The tide was pushing Vindictive farther out of position. Two commandeered Liverpool ferry boats – Daffodil and Iris – had followed Vindictive to the mole and somehow survived the coast artillery’s fire. Daffodil pushed the cruiser alongside the mole, against the tide. Iris tried to land its Royal Marine reinforcements onto Vindictive.



HMS Vindictive steaming toward Zeebrugge, April 22, 1918. This image shows the full extent of the modifications for storming the mole, including the multiple brows and ramps, the splinter mat-armored foretop, the highest point of the ship (with machine guns and quick-firing cannons). Forward of that is the conning tower (where Capt. Alfred Carpenter was) and forward of that was a mount for a large flamethrower (another is aft). These were put out of action by German shellfire before they could be used. Smoke from only the after stack shows that the forward boilers have been secured. Author’s collection


The German guns, pounding the Vindictive, had not seen the obsolete British submarine C3. Running on the surface, it rammed the viaduct’s supports. It had been packed with 5 tons of explosives. Its skeleton crew set the delay fuse. Under heavy fire, they took to a small boat.

The viaduct exploded in an orange blossoming of flame. Leading Seaman William Cleaver wrote, “the boat rocked and swayed as though possessed. Flames shot up to a tremendous height. In their glare was visible a great break in the mole.”

HMS Thetis, Intrepid, and Iphigenia, the three blockships, emerged from the smokescreen. Their mission: to run through German gunfire to the mouth of the canal where it emptied into Zeebrugge harbor. Under heavy fire, Thetis’ screws caught in a harbor defense net. Prevented from turning broadside across the channel, Thetis grounded on a sandbank.  Intrepid, turning broadside to block the channel, discovered it to be broader than the blockship was long. Iphigenia got closer to the canal lock gates, but had not been ordered to ram them. The crews, escaping in small boats, were picked up by motor launches.



HMS Vindictive after Zeebrugge, showing her funnels riddled with machine-gun fire from the German defenses on the mole. Library of Congress


On the mole, Marines and sailors had been fighting a savage close-quarters battle. On Vindictive, Carpenter experienced “the terrific noise, the darkness, the bursting of shell and the hail of machine-gun fire.” He sounded the recall signal. Carrying their wounded with them, the survivors made a fighting withdrawal to Vindictive and the two ferryboats, all somehow still afloat. The destroyer HMS North Star, covering the withdrawal, closed in, firing guns and torpedoes. It was hit repeatedly by the coast guns and started to sink.

Some 150 minutes after the first shots were fired, the Zeebrugge raid was over. Keyes received bad news from Ostend. The two blockships, HMS Sirius and Brilliant, had been scuttled without reaching their planned locations; the plan had not provided navigators familiar with Ostend harbor for the volunteer crews. German resistance there had been less intense; Ostend had no equivalent of the heavily fortified mole and did not require an assault to suppress the defenses. The small German coastal U-boats and torpedo boats could use the lateral inland canals and the unblocked Ostend exit to go to sea.


After the Raid

Despite the loss of more than 600 men killed, wounded, and missing – German casualties had been light – Keyes was committed to using what remained of the raiding force to close Ostend, even though the element of surprise was obviously lost. Twice more, Keyes and the force went back to Ostend. On the second attempt, on the night of May 11-12, Vindictive, hastily patched together as a blockship, was scuttled in the channel of Ostend harbor. But a single blockship was not enough to block it. A third attempt, planned for June, was cancelled.



HMS Vindictive after Zeebrugge, showing the damage inflicted by the German coast defenses as well as the modifications such as the brows. The fenders were to prevent damage when alongside the mole. Library of Congress


The boost to Allied morale from Zeebrugge was considerable. Winston Churchill – then Britain’s Minister of Munitions – wrote that it “may well rank as the finest feat of arms in the Great War.” The heroism of those involved had been astounding. Eleven of the raiders – including Carpenter – received the Victoria Cross, Britain’s highest award for valor, more than in any other comparable-sized action in the war.

The Germans immediately set about repairing the damage, using dredgers to remove obstacles and create new channels. British naval bombardments and air attacks on the ports inflicted more damage and hindered repair efforts. The raid never completely blocked U-boat operations from Zeebrugge and Ostend. But the canal linking the two ports was effectively closed to larger U-boats and destroyers for 50 of the 70 days following the raid, by which time the British had been able to reinforce the defenses of the Straits of Dover. The Belgian U-boat bases remained operational until the last weeks of the war, with the victorious Allied armies advancing and the German navy, its morale collapsing, starting to mutiny.


1918’s Lessons

The motivation and courage of those who carried out the Zeebrugge raid proved not to be a substitute for flaws in the improvised planning, intelligence preparation of the battlespace, and the training and rehearsal leading up to it. Tremendous heroism did not prevent heavy losses and did not yield decisive results. In the years that followed, the British – especially the Royal Navy – turned away from special operations. This proved to be a costly decision when, in 1940, Britain, standing alone against Nazi Germany, had to hastily re-create a special operations capability. Zeebrugge provided a model for direct attack special operations such as the 1942 raid on the French port of St. Nazaire.



An aerial photograph showing the aftermath of the Zeebrugge raid. British blockships lie from left to right: HMS Intrepid, HMS Iphigenia, and, farthest out, HMS Thetis. Imperial War Museum


Similarly, the small combatants – coastal motorboats and motor launches – that had played a major role in the raid were not part of the post-1918 Royal Navy. Again, they had to re-create this force when World War II loomed.

A century later, Zeebrugge’s lessons are valuable to today’s special operations forces. The direct attack mission remains a core special operations competency in all domains – land, air, and sea. Direct attack is seen as vital for countering the weapons of mass destruction that in the hands of state and non-state threats present a greater existential threat than the Kaiser’s U-boats did in 1917. Similarly, potentially powerful morale effects remain an important consideration in planning and executing special operations. The German navy’s successful defense of Zeebrugge and effective repair efforts did not prevent that service’s mutinies following within months.



Zeebrugge demonstrated that a special operations capability cannot be improvised. The hasty planning by Keyes and his staff – experienced naval officers but with no special operations experience – suffered from the need to maintain a high level of operational security. Planning and training alike were carried out in the dark, reflecting the limited intelligence support available. In addition, they didn’t understand the difficulty of what they were asking the raiders to do under heavy fire. The all-important intelligence and targeting, especially the capability to identify where the raiders might do the most damage and how the Germans might be able to mitigate the damage, was lacking.

The raiders themselves had been excluded from the planning process. They had been unable to socialize or refine Keyes’ plan. The raid’s dependence on smokescreens, the vulnerability of the unarmored landing gangways and ramps and the unprotected personnel on Vindictive, the choice of blockships and the locations where they were to sink: All these proved on the night to be costly – yet avoidable – flaws in the planning. The raiders, brave and motivated, lacked either special operations experience or even training in defeating fortified machine guns using the fire-and-movement tactics that the British Army had evolved on the Western Front.


Capt. Alfred Carpenter, who volunteered to command HMS Vindictive in the raid, earned one of the 11 Victoria Crosses awarded to participants in the raid. He had no experience with special operations or with the waters of the Belgian coast. Library of Congress


Zeebrugge could have provided cautionary lessons to those that planned the Son Tay raid in 1970 or the Iran hostage raid in 1980. These raids were also both carried out by improvised – though high-quality – forces. The overall leaders were not experienced in special operations. Intelligence that could have made a difference between failure and success was not made available to the raiders or planners. Operational security considerations limited the raids’ training and coordination. At too many points in the plan, something failing could doom the entire mission. Multiple “moving parts” in a high-friction environment result in a high-risk operation.

Zeebrugge was planned and executed with only a limited understanding of what effective special operations – including direct attack – require to be successful. But the spirit and courage of those who carried out the raid, as well as the impact on morale that these qualities achieved, remain as important to today’s professional special operations forces as they were to the hastily improvised force of volunteers that attacked Ostend and Zeebrugge on April 23, 1918.


This article was first published in the Special Operations Outlook 2018-2019 Edition publication.