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Posted on Aug 29, 2011 in Boardgames

CDG 46 – Zeebrugge Raid, 1918

By Armchair General

The September 2011 issue of Armchair General® presented the Combat Decision Game “Zeebrugge Raid, 1918.” This CDG placed readers in the role of British Royal Navy Vice Admiral Roger Keyes, commander of the Dover Patrol during World War I. Keyes’ mission in April 1918 was to devise a plan to raid the German-held port of Zeebrugge, located in Belgium on the North Sea coast near the English Channel. The goal of the raid was to block the entrance to the Bruges-Zeebrugge Canal and thus reduce the German U-boat threat to Britain’s vital Atlantic convoys. About one-third (40-50) of Germany’s deadly “Grey Wolves” were based at Bruges and transited the canal en route to their Atlantic Ocean “hunting grounds.”

Keyes was convinced that to give the blocking cruisers the best chance to reach the canal entrance, he had to find a way to divert the German defenders’ attention away from the raid’s main objective. Thus he chose to land an assault force of armed sailors and Royal Marines on Zeebrugge’s mole (Course of Action Two: Diversion). Although two blockships were successfully scuttled at the mouth of the canal, the Germans cleared a path for U-boat passage within a few days. (Petho Cartography)HISTORICAL OUTCOME
Keyes decided that the raid’s main objective, blocking the canal entrance, would have the best chance to succeed if the German defenders’ attention was drawn elsewhere (Course of Action Two: Diversion). Therefore, he included in his raiding force a diversionary attack force of 200 armed sailors and 400 Royal Marines supported by the cruiser HMS Vindictive to assault the German positions on the mole while the three blocking cruisers – Intrepid, Iphigenia and Thetis – entered the harbor and raced for the mouth of the canal. Two coastal submarines, C1 and C3, would be blown up under the viaduct to prevent enemy reinforcements from counterattacking onto the mole.

At 10 p.m., April 22, 1918, Keyes’ 75-ship armada (the raiding force ships plus the protecting warships and support vessels) reached a location 16 miles off Zeebrugge, the raiders’ launching point. At 11:56 p.m., HMS Vindictive burst out of a thick smoke screen laid by the armada’s support vessels and steamed toward the Zeebrugge mole only 300 yards away. Surprised and stunned, the German gunners had no time to react before Vindictive’s portside batteries opened up and blasted the mole from a distance of barely 50 yards. The ferryboats pushed Vindictive close to the mole, and the armed sailors and Royal Marines disembarked and then struggled through barbed wire to attack the German positions. (See Zeebrugge Raid map.) As Vindictive’s gunners engaged enemy artillery and the guns of German torpedo boats anchored on the far side of the mole, the landing party continued to fight its way along the mole against heavy fire. While the diversionary attack diverted the Germans’ attention, submarine C3 was blown up under the viaduct, creating an impassable 60-foot gap (C1 parted its towrope crossing the channel and did not take part in the raid).

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Meanwhile, the three blocking cruisers left the safety of the smoke screen and entered Zeebrugge harbor with HMS Thetis leading the way. Unfortunately, Thetis fouled its propellers and drifted back into the main channel – making a perfect, nearly stationary target for German guns – where it was scuttled by its crew. Yet Thetis and the diversionary attack helped Intrepid and Iphigenia make it across the harbor to the canal entrance, where they were successfully scuttled in blocking position.

Royal Navy motor launches and small boats rescued most of the crewmen from the submarine and blockships, but casualties were heavy among the armed sailors and Royal Marines who landed at the mole. The Royal Marines of 4th Battalion were especially hard hit, losing 118 killed and 202 wounded. Royal Navy causalities were 101 killed, 154 wounded and three captured.
Although the Zeebrugge raid blocked the canal entrance, German engineers reacted quickly and cleared a path so that U-boat traffic was able to resume within a few days. Nonetheless, the raid’s success boosted Britain’s homefront morale, as it was a rare and desperately needed victory at a time when Germany’s Kaiserschlacht Spring Offensives (March-July 1918) on the Western Front threatened to collapse the Allied line.

A similar Royal Navy raid on April 23-24 at Ostend, Belgium – another port transited by Bruges’ U-boats – was a total failure, and a second Ostend raid on May 10 achieved only limited success.

ACG judges based their selections for winning Reader Solutions and those receiving honorable mention on submissions that chose Course of Action Two: Diversion, or those whose explanations demonstrated a solid understanding of the key points of a naval raid. (See “After Action Report.”) The key to getting the blocking cruisers into position was reducing the volume of enemy fire enough to give the ships a fighting chance to reach the canal entrance to be scuttled. The diversionary assault on the mole – although it risked heavy casualties among the sailors and Royal Marines – distracted German gunners, focused enemy attention away from the main objective, and reduced the volume of fire directed at the blocking ships.

Course of Action One: Full Block not only created a serious traffic control problem in the narrow confines of the harbor with the three blocking cruisers and two submarines all trying to reach the canal entrance at the same time, it also permitted the Germans to concentrate their fire on the closely packed group of ships. With no diversion to distract the defenders, this plan jeopardized the blocking ships’ efforts to reach the canal entrance.

Course of Action Three: Harbor Assault was likely the worst plan under the circumstances, as it asked too much of the raiders. The German defenses at Zeebrugge were too extensive and spread out for a raiding force to quickly overwhelm, and any attempt to do so likely would have fatally detracted from the raid’s main objective of blocking the canal entrance.


  • Become thoroughly familiar with deepwater approaches to the target and the hydrography of the immediate target area.
  • Gather all possible intelligence about the enemy defenses – troops, reserve forces, obstacles, gun emplacements, naval defense assets, etc.
  • Carefully plan access and egress routes to minimize the raiders’ exposure to enemy fire.
  • Conduct raid rehearsals so that all participants fully know their roles and duties.
  • When possible, execute diversionary actions to shift enemy attention from the raid’s main objective.
  • Strike hard and fast, focusing on the main objective, then rapidly withdraw to reduce exposure to enemy fire and counteractions. 


  1. There is another important reason why COA#1 is unwise. As the actual events show, a spare blocking ship would have been good to have, however the submarines are highly unsuitable. They are too small; while each of the three Apollo-class cruisers intended as blocking ships displaced 3700 tons floating, a C-class submarine only displaced 320 tons even when submerged. It is thus significantly less than a tenth och the size of the cruisers. It is also much slower 20 knots versus 13 knots (surface speed) and using them with the cruisers would slow down the assualt by a third. Also I assume submarine personell has little training in moving in formation with other ships so there would be a coordination problem.


  2. I disagree with both the conclusion of the CDG and the reasons for why COA #1 was unsuitable. Reading the historical outcome as posted on other web pages, the raid was actually a tactical failure, regardless of the boost to English morale. It is unlikely that had the raid not been conducted at all that the Enlish homefront would have just folded under the weight of the German’s offensve in 1918. The diversion cost 200+ casualties which, in anyones’ opinion, militarily or otherwise, is attrocious if the only gain is a ‘boost to moarale.’ Moreover, the use of the sailors and marines on the mole is just further evidence of the propensity of commanders during WWI to recklessly throw the lives of their soldiers and sailors away.
    It is arguable that had COA #1 been rehearsed and executed the problems with sailing in formation and speed would have been identified, orrected and accounted for. Using a diversion is a great tactic, when the battlefield is a little more dispersed. But when the confines of the area are so small, as in Zeebrugge, than a diversion is of little use as all it serves to do is alert the defenders.
    Again, the raid was a failure, as the Germans were using the canal/port within a few days.

    • I agree with Mark questioning if it was really worth it in retrospect. Even with the best tactic, the result was mixed (tough that was possibly caused by a bit of bad luck with the third blocking ship that did not get into place). It should probably be seen as a sign of desperation caused by Germany’s successful submarine warfare.

      However, I disagree with his statement: “than (sic!) a diversion is of little use as all it serves to do is alert the defenders.”

      Like the solution says, the diversion took away much of the volume of fire from the blocking ships. As for as alerting the defenders, we can assume they knew something was up as soon as they saw the smokescreen.


  3. It did not work, but was a try, to shorten the war. Now this raid accomplished nothing. 200 sailors and marines killed for not return. Three ancient cruisers due for the scrap heap were not so much of a loss. Nice propaganda, but were there better campaigns to have planned. What about attacking Helgoland and bottling up the High Seas Fleet?

  4. As always, the British High Command, including the Admiralty were having a good time fighting a past war. The raid on Zeebrugge would not have been out of place in the Napoleonic Wars, say Cadiz with fireships to bottle up the Spaniards. The plan was doomed from the start, using out of date methods to accomplish something almost meaningless. Did the British really believe that the Kaiser’s engineers, in a country fighting a total war, would not be able to clear a few blockships? The Great War required innovation and from the Dardanelles to Gallipoli to the line of battle at Jutland, the Admiralty, with Churchill as First Lord, continually showed their inability to deal with modern warfare.


  1. CDG Command Center » Armchair General - [...] September 2011 Zeebrugge Raid, 1918 PDF Pullout Historical Outcome [...]
  2. Tactics 101 078 – Lightning Strike: The Combat Raid » Armchair General - [...] The Raid on Zeebrugge. On 23 April, 1918, the Allied Navy initiated a daring naval assault on the Belgian …

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