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Posted on Jul 14, 2011 in Armchair Reading

CDG 46 – Zeebrugge Raid, 1918

By Andrew H. Hershey

Download pdf for larger image. Map by Petho Cartography.It is April 1918, and you are about to assume the role of Royal Navy Vice Admiral Roger Keyes, commander of the Dover Patrol. The German U-boat menace hangs over the ships that are expected to bring some 300,000 American troops to Europe by summer to join Britain, France and their allies in fighting Kaiser Wilhelm’s men—and, hopefully, breaking the long stalemate on the Western Front. The British Admiralty, after months of debate, has authorized an operation against Zeebrugge, Belgium, near which about one-third of all German submarines are based. The idea is to trap the "Grey Wolves" in their den by blocking the mouth of the narrow Bruges-Zeebrugge canal that the U-boats use to reach the Atlantic. You are responsible for devising the operational plan for the raid to block the canal at Zeebrugge.

The town has been in German hands since 1914, and the occupiers have turned it into a daunting fortress. Surrounding the harbor, from east to west, are two coastal artillery batteries, one with two 105 mm guns and one with four 150 mm guns. An anti-aircraft battery of four 37 mm guns, a battery of four 210 mm guns and another of four 170 mm guns add to the threat. Additionally, along the mole, facing out to sea, are two 37 mm anti-aircraft guns and a battery of six 88 mm guns. At the mole’s eastern tip is a six-inch mortar for firing illumination shells, and on the mole’s leeward side pointing into the harbor are three 150 mm guns.

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Zeebrugge’s infantry garrison has prepared trenches and sandbagged machine-gun positions ringed by barbed wire entanglements along the mole and the coastline to protect the artillery emplacements against a ground attack.

Ship access to the restricted waters of the inner harbor is only possible through the narrow opening between the mole and the coast. The North Sea’s notorious tides and currents constantly shift shoals and sandbars that can trap or ground unwary vessels. Once inside the harbor, blocking ships heading for the mouth of the canal must run a gauntlet of artillery, machine-gun and small-arms fire.

Your forces for the operation against this formidable position include 1,700 sailors and Royal Marines and 75 ships of various sizes, which are organized into a large supporting force and a much smaller raiding force. The supporting force, your Dover Patrol, consists of a destroyer squadron and two flotillas—one made up of small, fast and lightly armed Coastal Motor Boats (CMB), and the other composed of slightly larger Motor Launches (ML). The flotilla’s mission is to lay close-in smoke screens to cover the raid, help evacuate raiding crews, and provide protection from German E-Boats. The 11 ships in the destroyer squadron will screen the operation from any approaching German warships and, if necessary, provide naval gunfire bombardment on Zeebrugge.

The raiding force consists of eight His Majesty’s Ships: four obsolete cruisers, Vindictive, Intrepid, Iphigenia and Thetis; two old coastal submarines, C1 and C3; and two passenger ferries, Iris II and Daffodil. The crews include 200 sailors who have volunteered to fight as infantry, and 400 Royal Marines of 4th Battalion, Royal Marine Light infantry. The raiding force’s mission is to put the "cork in the bottle" by sinking Intrepid, Iphigenia and Thetis at the mouth of the canal to block it. These blockships have been stripped of all usable equipment, rigged with scuttling charges, and loaded with concrete and rubble ballast to prevent the enemy from easily raising them to clear the entrance.

Diagram of blocking ships; Green shows concrete, blue is water ballast, red is explosive charges.

With the raid set to take place the night of April 22–23, 1918, you have been summoned to Admiralty headquarters in London to brief the current First Sea Lord, Admiral Sir Rosslyn Weymss, and other senior Royal Navy officers on your plan for conducting Operation ZO. Weymss, immediately getting down to business, directs you to a large map of Zeebrugge mounted on the office wall.

"Sir, gentlemen," you begin, "I have devised three possible courses of action. With each, the role of the Dover Patrol supporting force remains the same: smokescreen, protection and evacuation assistance. I welcome your comments and guidance regarding these plans."

Course of Action One:
"The first course of action is to concentrate our resources on the main objective, blocking the mouth of the canal. Under cover of darkness and the smokescreen, the three cruisers and the two submarines will rush into the harbor, proceed at flank speed to the canal, and then scuttle themselves within the narrow confines of the canal entrance. Vindictive will lay close off the seaward side of the port entrance and provide naval gunfire support to cover the CMBs, MLs and ferries as they race in and evacuate the crews of the cruisers and subs. The armed sailors aboard the ferries and the Royal Marines on Vindictive will serve as a ‘floating reserve force’ to be used only if absolutely necessary to cover the evacuation."

Weymss, as the senior officer present, speaks first. "Roger, although this plan focuses our assets on the main objective, blocking the canal entrance, the confined geography of Zeebrugge port leads me to suspect you will have a ‘traffic control’ problem—five blocking ships all jockeying for position in a mad rush."

Commodore Reginald Tyrwhitt breaks in. "With respect, sir, although Admiral Keyes did not say so outright, I expect he realizes that, given the number of enemy guns ringing the inner harbor, not all of his blocking ships will safely reach the canal entrance. Likely, he is sending five ships in the hopes that at least two or three get through."

Your silence neither confirms nor denies Tyrwhitt’s comment—although most in the room suspect it hit the mark. You quickly move on to presenting your next course of action.

Course of Action Two:
"The second plan I am considering," you continue, "is to increase the chance of the three blocking cruisers safely getting into position at the canal’s mouth by landing a diversionary force of armed sailors and Royal Marines on the mole. Vindictive and the two ferries will disembark the men on the seaward side of the mole, where they will attack and destroy the enemy artillery positions. Meanwhile, the two submarines—rigged with explosive demolitions—will sail under the viaduct and detonate their charges, destroying the viaduct and preventing German reinforcements from moving on the mole. Once this diversionary attack is well under way, the three blocking cruisers will enter the harbor, steam to the entrance of the canal, and scuttle themselves to block it. CMBs and MLs will rush in and evacuate the blocking cruisers’ and submarines’ crews, while the diversionary force re-embarks on Vindictive and the ferries to quickly escape out to sea."

Admiral Reginald Bacon, your predecessor in Dover Patrol command, responds, "Roger, the diversionary assault on the mole presents a number of practical problems for the armed sailors and Royal Marines, not to mention the difficulties the Vindictive and the ferries will encounter just getting close enough to land the assault force. If the enemy reacts quickly, the ships carrying this force could face a blizzard of artillery, machine-gun and small-arms fire that could prevent the men from even reaching the mole."

Weymss somewhat impatiently replies, "Reginald, not to be too callous where our men’s lives are at stake, but the attack on the mole is a diversion. Whether or not the assault force actually seizes the mole is entirely irrelevant—as long as the action diverts the enemy’s attention away from our men getting the blocking ships in place."

Course of Action Three:
"The third course of action," you explain, "is to take full advantage of the raid by destroying as many enemy gun positions as possible while still accomplishing our main objective of blocking the canal entrance. As in the second plan, Vindictive will land the Royal Marines on the mole while the submarines destroy the viaduct, but this time the ferries will land the armed sailors near the largest gun positions along the harbor’s coastline. The mission of the assault force will be to destroy the German guns ringing the harbor. When the attack is well under way, the three blocking cruisers will enter the harbor, sail to the canal entrance, and scuttle themselves there. CMBs and MLs will evacuate the blocking cruisers’ and subs’ crews, and the assault force will re-embark on Vindictive and the ferries after destroying the targets."

Tyrwhitt, a former torpedo boat and destroyer commander who at the battles of Heligoland Bight, Dover and Jutland earned a fleet-wide reputation as perhaps the most offensive-minded officer in the Royal Navy, appears excited at the prospect of carrying out this plan. "I say, this is more like it!" he declares. "Let’s pitch into them and really make this raid a big show! If can take out most or all of Zeebrugge’s guns, we’ll make the job of evacuating our men form the blocking ships, subs and assault force much easier. Moreover if—God forbid—our efforts to obstruct the canal are only partially successful, or if the Germans are able to clear the entrance quickly, we will have much reduced Zeebrugge’s defense if we have to go back in and do it all over again."

Admiral Lewis Bayly speaks up. "I realize that some of you are more keen on this raid than I am—a few have even suggested that the raid be expanded into an all-out assault by a full division of ground troops to seize the port as a means of outflanking the stalemated Western Front. Yet I advise that we proceed with due caution and keep foremost in our minds the main objective: blocking the canal entrance to prevent U-boat egress. I fear that expanding the raid to a full-out attack on the harbor is foolhardy, as this asks too much of our ships and men."

Weymss ends any further discussion by rising and addressing the assembled officers. "Gentlemen, thank you for your comments, all of which I am sure Admiral Keyes appreciates and will take into consideration. Roger, please inform me tomorrow morning which course of action you have chosen."

Admiral Keyes, which of the three plans will you choose? Or has the discussion led you to conceive of another possibility?

Click here to download the pdf of Command Decision Game # 46, Zeebrugge Raid, 1918. Submit your answer and you might win a prize from Armchair General!

This text is an abridged version of Command Decision Game #46, written by Andrew H. Hershey. The full text appears in the September 2011 edition of Armchair General magazine, where you’ll also find additional interactive articles based on British paratroopers on D-Day and on German commander Colonel-General Gotthard Heinrici’s mission to stop the Soviet onslaught near Berlin, 1945. On newsstands now.



  2. Why does the CDG section not have it’s own listing on the home page?
    Why does the highlighted email adddress for sending in solutions not do anything when I click on it?

    • Putting a link directly to the CDG section from the ACG home page was a good suggestion, Steve. You’ll now find Command Decision Games as an option in the drop-down menu under Games in the menu bar. Thanks!

      As for the email address, it isn’t a link. Notice that it spells out “at” and “dot” in the address rather than using the symbols for those words, in order to combat spammers. You’ll have to type in the address manually the first time you email a solution – but after that your email program should remember the address for you. To make it clearer that this is not a link we’ve changed the color of the type from blue to red.


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