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  • Writer's pictureMatthew Camilleri

The Zeebrugge Raid

Updated: Apr 13, 2023

On 23rd April 1918, the Royal Navy carried out a daring amphibious raid on the German-held port of Zeebrugge, in Belgium, in an attempt to prevent it from being used by German U-boats, which posed a serious threat to Allied shipping. Although the operation was only partially successful and came at a heavy cost, the participants demonstrated exceptional bravery, which was reflected in the long list of gallantry medals awarded in the raid’s aftermath.

The U-boat Menace

Following Germany's resumption of unrestricted submarine warfare in February 1917, Britain was in danger of being starved into submission. In April of that year, a record 881,027 tons of Allied and neutral shipping were sunk by the U-boats. That same month, the United States entered the war, due to outrage at the German tactics, but U.S. troops would not begin major combat operations on the Western Front until the summer of 1918. The British knew that they had to deal with the U-boat problem quickly, or American involvement might come too late.

In May 1917, the British resorted to the convoy system, where merchantmen were grouped together and were provided with a naval escort. This system proved quite effective, while gradually, new technology weapons were also developed to help combat the U-boats, such as depth charges and hydrophones. Yet many believed that the most effective method was to strike directly at the bases that the U-boats were operating from.

Zeebrugge and Ostend

While the main U-boat bases in Germany were beyond striking range, an attack on Zeebrugge and Ostend, which served as satellite ports for the city of Bruges, in German-occupied Belgium, appeared to be more feasible. Bruges had been captured by the advancing German divisions during the Race to the Sea in October 1914 and had been rapidly identified as an important naval base for the Kaiserliche Marine. Extensive facilities were immediately built to provide support for several flotillas of destroyers, torpedo boats, and U-boats. Its location, 9.7 kilometres inland, protected Bruges from naval bombardment and amphibious assaults, whilst the German vessels based there could travel down a system of canals to access the English Channel via the two sea entrances at Zeebrugge and Ostend.

German vessels based in Bruges could travel down a system of canals to access the English Channel via the two sea entrances at Zeebrugge and Ostend

In early 1917, Vice-Admiral Sir Reginald Bacon, the commander of the Dover Patrol, devised a plan to destroy the lock gates at Zeebrugge by bombardment with the 15-inch guns of the monitors HMS Erebus, HMS Terror, and HMS Marshal Soult. After several aborted attempts, the operation eventually commenced on the evening of 11th May, but soon had to be abandoned due to poor visibility and a change in wind direction, which cleared the British smoke screen, thus making the ships visible to the German shore batteries. Subsequent aerial reconnaissance revealed that only minor damage had been caused. Two similar operations were carried out against Ostend on 5th June and 22nd September, and although they were slightly more successful, it was clear that such attacks were having little effect.

Bacon also assisted in the planning of Operation Hush, which was to consist of amphibious landings by the three brigades of the British 1st Division around Middelkerke, at the northern extremity of the Western Front, and further down the coast from Ostend and Zeebrugge. These landings would be supported by an attack from Nieuwpoort and the Yser bridgehead, but this part of the plan was foiled when the Germans carried out a spoiling attack, known as Unternehmen Strandfest, during which they captured part of the bridgehead over the Yser and annihilated two British infantry battalions. Operation Hush was also dependent on the British advance in the Third Battle of Ypres, and after several postponements, it was finally cancelled on 14th October 1917, as the advance at Ypres had still not met the objectives required for the operation to go ahead.

The Plan

As unrestricted submarine warfare continued, finding a way to close the ports became increasingly urgent, forcing the Admiralty to seek ever more radical solutions. In October 1917, Rear-Admiral Roger Keyes was appointed director of the Plans Division at the Admiralty and immediately started planning a new operation against Zeebrugge and Ostend. In January 1918, now Acting Vice-Admiral, Keyes succeeded Bacon as commander of the Dover Patrol and soon submitted his plan for a daring amphibious assault that was intended to block the sea exits at the two Belgian bases, thus trapping the German vessels inside. This was to be achieved by sinking two obsolete, concrete-filled Apollo-class cruisers, manned by skeleton crews, in the canal mouth at Ostend, and three more at Zeebrugge, before their crews would be extracted by motor launches.

In October 1917, Rear-Admiral Roger Keyes was appointed director of the Plans Division at the Admiralty and immediately started planning a new operation against Zeebrugge and Ostend

Of course, getting the blockships into position would be challenging, as they would be vulnerable to fire from the German shore batteries on their approach. A particular problem was posed by the Zeebrugge mole, a large concrete breakwater, about 1.6 kilometres long, built before the war. When the Germans had captured the port in 1914, they built several gun batteries along its top, and it was clear that these would have to be silenced if the blockships were to reach the correct position before they could be scuttled. The modified obsolete cruiser HMS Vindictive would thus approach the mole under a smoke screen and disembark a battalion of Royal Marines, who would take out the gun batteries and clear the way for the blockships.

The plan for the attack on Zeebrugge

At the same time, two old submarines, also with skeleton crews and loaded with explosives, were to be driven into the viaduct connecting the mole to the shore, in order to blow it up and prevent German reinforcements from reaching the mole. The monitors HMS Erebus and HMS Terror would provide naval gunfire support, while coastal motor boats and motor launches would be used to attack the defences, rescue the blockship crews, and put down smokescreens.


In February, the plan was formally approved by the British Admiralty, and preparations immediately got underway. Since the Royal Navy of 1918 had no existing special operations forces, men had to be found to make up both the crews and the assault forces. An urgent appeal was made for volunteers "to perform a hazardous service", although the nature of it was not disclosed, in order to maintain secrecy. On 24th February, the 4th Royal Marine Battalion was formed specifically for the mission. It was composed of 30 officers and 660 men from the Royal Marine Light Infantry, together with a detachment of two officers and 58 men from the Royal Marine Artillery.

The modified obsolete cruiser HMS Vindictive was to transport a battalion of Royal Marines, who would take out the gun batteries on the mole, thus clearing the way for the blockships

HMS Vindictive, as well as the five cruisers that were to be used as blockships, including the three earmarked for Zeebrugge - HMS Thetis, HMS Intrepid, and HMS Iphigenia - were readied at Chatham. The blockships had all unnecessary equipment, including their masts, stripped out, before they were filled with concrete. Two Mersey ferries, requisitioned by the navy and renamed HMS Daffodil and HMS Iris II would be towed across the channel by Vindictive before they were to assist her in landing the troops on the mole. They were specially fitted out at Portsmouth, together with the submarines HMS C1 and HMS C3, which were to target the viaduct.

HMS Iris II was one of two former Mersey ferries that were requisitioned by the Royal Navy to participate in the Zeebrugge raid

Success in the upcoming raids would depend on a number of factors, including the state of the tide and weather, a favourable wind for the smoke screen, and the absence of fog. The first opportunity presented itself in April, and an attempt was made on the 11th but had to be cancelled at the last minute after the wind direction changed, making it impossible to lay the smoke screen needed to cover the ships. Another attempt was made on 13th April, but it also had to be called off due to strong winds. The Admiralty considered cancelling the operation altogether, fearing that the element of surprise might have been lost, but Keyes was able to persuade them to try again, on the night of 22nd/23rd April.

The Raid

On the evening of the 22nd, the force sailed for the third time, crossing the English Channel under cover of darkness. The monitors began a diversionary bombardment of Zeebrugge and Ostend at 11.20 pm. Similar bombardments had been carried out on previous nights so that the enemy would not notice anything different. At 11.40 pm, the fast boats began laying their smoke screen. Unfortunately, the smoke, coupled with the engine noises, alerted the German defenders. To make matters worse, as Vindictive approached the mole, the wind changed direction, blowing the smoke away and making her visible to the German gunners. Star shells lit up the whole area, giving the shore batteries a clear view, and as searchlights came on, perfectly illuminating the raiding force, the defenders opened up with everything they had.

Royal Marines disembarking onto the mole from HMS Vindictive under heavy fire

Vindictive finally pulled up alongside the mole at one minute past midnight on 23rd April, St. George’s Day. Yet, having been battered by gunfire on the approach, she reached the mole in the wrong position, some 275 metres away than originally planned. She was followed a few minutes later by Daffodil and Iris II. Daffodil's primary duty was to push Vindictive up against the mole, to enable her to be secured, after which she was to pull alongside the mole herself and disembark her own Marines. In the end, her Marines had to disembark from her bows onto Vindictive, as it was found essential to continue to push the larger vessel onto the mole throughout the action. Iris II was also unable to land her Marines directly onto the mole, so she too went alongside Vindictive to enable the attacking force to land across her, although only a few of the men succeeded in doing so.

By this point, heavy losses had already been sustained, particularly by the crews manning the guns on Vindictive, but also by the storming and demolition parties, who were expected to charge onto the mole over specially built gangways before silencing the guns and inflicting as much damage as possible. Yet, even before they had the chance to do so, the heavy enemy fire wiped out some of the platoons and left others with only a fraction of the men tasked with carrying out their objectives. Most of the gangways were destroyed before they could be used, and to make matters worse, the fact that they had been landed in the wrong place, coupled with the heavy losses, seriously disorganised the attacking force. Because they had been landed much further away from the guns that they were meant to destroy, and the ground in between was now being swept by machine gun fire, they were unable to complete their task.

The Viaduct

The submarine HMS C3 was successfully rammed into the viaduct’s supports, whereupon the crew set the delay fuses of the explosives packed in the bow before they were taken aboard a launch

In the meantime, the German guns, concentrating their fire on Vindictive, had not seen the submarine C3 running on the surface towards the viaduct. Although C1 had parted with her tow during the passage from Dover, arriving too late to take part in the operation, Lieutenant Richard Sandford, commanding C3, was now manually guiding his submarine towards the target, having decided not to rely on the automatic gyro-control system which would have enabled the crew to abandon the vessel before it struck the target. C3 was successfully rammed into the viaduct’s supports, whereupon the crew set the delay fuses of the explosives packed in the bow before they were taken aboard a launch. A few minutes later, at 12.15 am, the five tons of explosives blew up, taking most of the bridge with them.

The Blockships

The assault on the mole was of course mainly intended to draw the Germans' attention away from the main objective of the raid - the blocking operation. The three blockships were making their way towards the entrance of the canal. Unfortunately, the failure to subdue the German guns resulted in Thetis, Intrepid, and Iphigenia coming under heavy fire. Thetis, leading the way, ended up with both her propellers caught up in a harbour defence net, and, badly damaged by enemy fire, had to be scuttled prematurely, before reaching the canal entrance. By 12.45 am, Intrepid and Iphigenia had also been scuttled in the narrowest part of the canal, before their crews were picked up by motor launches.

Whilst HMS Thetis had to be scuttled prematurely, before reaching the canal, HMS Intrepid and HMS Iphigenia were scuttled in the narrowest part of the canal

With the main objective of the mission having been completed, the withdrawal was sounded, and the storming and demolition parties, who had been fighting a fierce, close-quarters battle for just under an hour, made a fighting withdrawal to Vindictive and the two ferryboats, all of which were somehow still afloat. More casualties were suffered at this stage, but by 1.15 am, the three vessels were clear of the mole and on their way back to Dover, though not before the destroyer HMS North Star, covering the withdrawal, was sunk after having taken a number of hits from the coastal guns.


Simultaneously with the raid at Zeebrugge, another blocking operation had been taking place at Ostend. Smaller and narrower than that at Zeebrugge, the Ostend canal was considered a secondary target and had fewer resources allocated to it. Unfortunately, the operation ended in complete failure when the two blockships, HMS Sirius and HMS Brilliant, ran aground after having failed to locate their objective and had to be scuttled in the wrong place.

As for the Zeebrugge raid, despite the boost to Allied morale that it provided, with Winston Churchill - then Britain’s Minister of Munitions - writing that it “may well rank as the finest feat of arms in the Great War”, the Germans immediately set about repairing the damage, using dredgers to remove obstacles and create new channels. Within just a few days, the port had been reopened to smaller vessels, including most submarines. On 10th May, the British undertook the Second Ostend Raid, in which Vindictive herself was used as a blockship, together with HMS Sappho. Although this operation proved somewhat more successful, it too failed to completely close off Bruges, with the Belgian U-boat bases remaining operational until the last days of the war, when the town was liberated by Allied land forces.

German officers aboard HMS Vindictive after she was herself sunk as a blockship during the Second Ostend Raid in May 1918

Despite the questionable results of the raids at Zeebrugge and Ostend, the heroism of those involved could not be called into question. Keyes received a knighthood, while a large number of gallantry awards were made to the raid participants, including eleven Victoria Crosses - Britain’s highest award for gallantry - as well as 31 Distinguished Service Orders, 40 Distinguished Service Crosses, 16 Conspicuous Gallantry Medals, 143 Distinguished Service Medals, and 283 Mentions in Despatches.

Yet the courage displayed by the participants proved not to be a substitute for flaws in the planning of the raid and did nothing to prevent heavy losses. Of the 1,780 men who took part in the raids at Zeebrugge and Ostend, 227 were killed and 356 were wounded, as opposed to eight Germans killed and sixteen wounded. Today, some of the casualties of the raid are buried and commemorated at Zeebrugge Churchyard and Memorial, Blankenberge Town Cemetery, and Oostende New Communal Cemetery in Belgium. Others whose bodies were recovered during the evacuation, or who died of their wounds later, were mostly buried at Dover (St. James’s) Cemetery. Those who have no known grave are commemorated on the Chatham, Portsmouth, and Plymouth Naval Memorials.

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