The Zeebrugge Operation

HMS Vindictive during the raid. Vindictive was an obsolete Arrogant-class protected cruiser, converted to act as the lead assault ship for the attack on the mole at Zeebrugge. She was fitted with additional armour, ramps for the troops and additional weaponry for fire support.

The blockships at Zeebrugge after the raid. Photographs such as this one, showing the blockships apparently in position, suggested that the operation against the canal had succeeded. However, the practical result was nothing more than a temporary inconvenience.

The Zeebrugge raid. This map shows just how formidable and well defended an objective the mole was, and how it shielded the entrance to the Bruges canal. It also indicates the planned and actual location of the assault ships and the blockships.

The final year of the war saw the Allies gradually overcome the U-boat threat while the naval blockade exerted increasing pressure on Germany, while the military balance on land showed signs of shifting. During 1918, one operation stands out – the Zeebrugge raid of 23 April 1918. Although militarily unsuccessful, it cheered public opinion in Britain and among her allies, and has entered national mythology.

Britain had tried various measures to hinder the U-boats, including those of the Flanders Flotilla. This force and a destroyer flotilla were based at Bruges, reaching the sea via a 13km (8 mile) canal to Zeebrugge or a 18km (11 mile) canal to Ostend. Repeated attempts were made to attack this network, but the base at Bruges was well protected against air attack or bombardment from the land, while the technology of the day made it impossible for attacking aircraft or bombarding warships to achieve the necessary accuracy to destroy the canal lock-gates at the two ports.

The alternative to bombardment was to launch an amphibious raid, but Zeebrugge and Ostend were well defended against any such landing. Both ports had many troops in well prepared defensive positions, as well as batteries of coastal artillery totalling over 30 guns at Zeebrugge and 40 at Ostend. The canal exit at Zeebrugge was further protected by the mole – a stone breakwater, over 1.6km (1 mile) long and some 75m (245ft) across its widest point. As well as helping to create the harbour, this edifice had been turned into a minor fortress, with six large artillery pieces, protected by machine guns and troops in defensive trenches.

Despite the difficulties involved, the importance of hindering the U-boats meant that a series of plans for attacking the Belgian ports was considered. These efforts accelerated when Rear Admiral Roger Keyes joined the Admiralty as Director of Plans in December 1917, bringing to the post the same energy and initiative that had seen him devise the raid into the Heligoland Bight at the beginning of the war. He began to modify previous concepts for a raid. Following his appointment as commander of the Dover Patrol on 1 January 1918, he was given responsibility for planning and leading the operation, which he code-named Operation Z.O.

‘The raiding force left home on22 April, the eve of St George’s Day. As the motley flotilla departed, Keyes signalled “St George for England”.’

The heart of the plan was for a number of old cruisers to be used as blockships, which would be scuttled to obstruct the canal exits into the sea at both Zeebrugge and Ostend; a thick smokescreen would help to cover their approach. However, at Zeebrugge the powerful artillery on the mole was ideally placed to blow the ships out of the water before they could reach their objective. Keyes therefore planned an assault against the mole from a converted cruiser. This element of the plan would primarily be a diversion to allow the blockships to approach the canal, but would also seek to inflict as much damage as possible on the military facilities on the mole. To support the assault an old submarine, filled with explosives, would detonate against the viaduct linking the mole with land, thus preventing the arrival of German reinforcements. Once the blockships had been manoeuvred into position, the forces on the mole would withdraw.

There were some doubts about whether the operation was feasible, but Keyes convinced the Admiralty that it was worth a shot. For the assault troops, he was assigned a battalion of Royal Marines and sought volunteers from among the crews of the Grand Fleet. The main assault ship was to be the old armoured cruiser Vindictive. In addition to her existing pair of 6in guns, she was provided with a formidable arsenal to support the attack, including three howitzers, two flamethrowers, batteries of mortars and several machine guns. She was also fitted with an additional upper deck to allow the assault troops to gain access to the parapet over the mole, which they would reach by specially designed ‘brows’ or ramps. Additional troops were to be carried in two Mersey ferries, Iris and Daffodil, chosen because their shallow draught would allow them to avoid mines, while their double hulls would make them very difficult to sink. They were given additional armour plate and protection against splinters in the form of sandbags and mattresses. Five old cruisers (three for Zeebrugge and two for Ostend) were chosen to act as blockships and were fitted with extra armour and with scuttling charges, as well as rubble and concrete to make them more difficult to remove. Finally, two old submarines, C1 and C3, were filled with explosives for use against the viaduct. The force comprised over 150 ships and some 1800 men.

The attack had to be conducted at high tide and, ideally, on a moonless night; hence there were only a few days each month when it was possible. Even then it would be challenging to get all of the ships to the right places at the right time because of difficulties of navigation in fast tides and shifting sandbanks, and against enemy fire over the final stages. The operation was launched on 11 April, but at a crucial moment the wind changed and blew away the smokescreen. Keyes took the difficult but necessary decision to call it off. One motor boat was lost, its crew being captured by the Germans. On 14 April, Keyes tried a second time, only to be frustrated once again by high seas and winds. Some senior officers felt the operation should now be cancelled as operational surprise had been lost, but Keyes was keen to press on and even dropped the requirement for a moonless night. The raiding force left home once again on 22 April, the eve of St George’s Day. Keyes was not one to overlook a possible reference to the country’s patron saint: as the motley flotilla departed, he signalled ‘St George for England’, to which the captain of Vindictive replied, ‘May we give the dragon’s tail a damned good twist.’

At 10.30pm the ships for the Ostend raid broke away from the main body. About half an hour later, monitors opened fired on the German coastal artillery batteries, while destroyers took up position outside both harbours to prevent German light forces from interfering with the unfolding operation. Shortly after 11pm the flotilla began to generate the smokescreen that was intended to cover the approach into Zeebrugge harbour. At first it succeeded; the German gunners opened fire when they heard engines approaching but could not see their targets.

At around 11.50pm the wind suddenly shifted, blowing away the smokescreen to reveal Vindictive steaming for the mole at a rapidly closing distance of a few hundred metres. The German heavy guns on the mole opened up at point-blank range and although Vindictive returned fire, several of her guns were quickly knocked out and the ship was heavily damaged. Many of the troops onboard were killed, including the naval officer commanding the sailors in the assault party, and both the commanding officer and the second-in-command of the embarked Royal Marines. In an effort to reduce the battering his ship was suffering, her captain shifted course and brought the old cruiser alongside the mole at one minute past midnight on St George’s Day. Unfortunately, although this action saved the ship from further damage, it meant that she came alongside a good 275m (900ft) from the intended spot. It had been hoped that from this location, behind the main defensive trenches, the mole guns could swiftly be stormed. The troops would now be exposed in the middle of the mole. Moreover, it proved difficult to hold the ship in place against a fast tide and lively swell. The grapnels that were to have secured her could not be attached to the mole, and she had to be held in position by Daffodil, which prevented many of the troops on the ferry from landing. The movement of Vindictive, heavy fire from the defenders and damage to the ramps meant that the assault troops got ashore more slowly than was anticipated. Many were killed or wounded before they could disembark. Iris got alongside the mole, but encountered similar problems getting her troops onto it because of the height of the parapet above her deck.

‘At a time when most news seemed bad, the Zeebrugge raid seemed a welcome sign that the Royal Navy was willing and able to conduct an audacious operation against the enemy-held coast.’

One part of the plan did unfold as intended; at about 12.20am the crew of the submarine C3 succeeded in navigating their way through the harbour and rammed the boat into the viaduct. They then disembarked into motor boats, as planned, and withdrew under increasing German fire. As they did so, the explosive-packed submarine detonated, destroying the viaduct and thereby isolating the mole, cutting communications and stranding any reinforcements.

Some assault troops did reach the mole and, despite the loss of most of their commanders, launched a number of spirited if sporadic attacks against the defenders. They came under heavy and effective fire from the garrison, protected in well prepared positions, and also from German destroyers moored on the far side of the mole. They could not reach either the artillery batteries or the other intended objectives; however, the main purpose of the assault was to provide a diversion to assist the blockships, which were the real point of the raid. This they achieved. Although the German guns engaged the blockships as they rounded the mole, their fire began later and was lighter than it would have been without the assault from Vindictive, Iris and Daffodil.

Thetis, the leading blockship, was supposed to enter the canal and then steam three-quarters of a kilometre (half a mile) into it, before ramming the lock-gates. As she approached the canal she was badly damaged by heavy gunfire, and then her propeller became entangled in an anti-submarine net. She became impossible to steer, so her captain detonated the scuttling charges. She sank just short of the canal entrance. However, she had drawn the fire of the German gunners and had cleared the nets, thus easing the approach of the other two blockships. The second, Intrepid, managed to steam into the canal and scuttle herself in the planned position across the channel. Unfortunately Thetis had been instructed only to attack the lock-gates; had Intrepid’s captain shown a little more initiative, he might have tried to ram them himself – though navigating the channel and avoiding the German fire would not have been easy. The third blockship, Iphigenia, also entered the canal, and, despite colliding with Intrepid as she manoeuvred into position, scuttled herself across the channel.

At 12.50am, as the blockships sank and their crews were taken off, the recall signal was sounded on the mole, and Vindictive re-embarked the survivors from the assault parties. As the ships withdrew, Iris was hit hard by the German artillery and the supporting destroyer North Star was sunk.

Casualties were heavy, with over 200 men killed (more than 50 by a single shell that struck Iris as she withdrew) and 400 wounded, with 13 captured. One destroyer and two motor boats were lost

The Ostend operation was simpler in conception, since there was no mole and hence no need or opportunity for a diversionary attack. Here, however, the German defenders were better prepared: the captain of the motor boat captured on 11 April was carrying a copy of the plans, so the Germans had been warned and moved two critical navigation buoys, making the already challenging task of approaching the canal all but impossible. The two intended blockships, Brilliant and Sirius, were both hit repeatedly by German fire, and then Brilliant ran aground. They could go no further so the scuttling charges were detonated, despite the blockships being some distance from the canal. Two later attempts were made, unsuccessfully, to block the canal at Ostend and a third was cancelled. No further attempt was made, largely because the increasing effectiveness of the Channel barrage made it unnecessary.

The British initially believed that the Zeebrugge part of the operation had succeeded: aerial photographs seemed to show Intrepid and Iphigenia lying across the main channel of the canal. In fact, while the blockships caused some initial disruption, the Germans were able to find ways of working around them within a few days and were making full use of the canal by mid-May. This might seem a distinctly modest success in view of the 600 casualties suffered.

The raid, however, was hailed as a triumph – albeit benefiting from considerable embellishment in official accounts. It had an enormously positive effect on morale in the Navy and in the hard-pressed Army, as well as on press and public opinion in Britain and her allies. At a time when most news seemed bad, with the German offensive on the Western Front gaining considerable initial success, the Zeebrugge raid seemed a welcome sign that the Royal Navy was willing and able to conduct an audacious operation against the enemy-held coast. The Admiralty initially baulked at the high number of medals recommended by Keyes – including no fewer than 11 Victoria Crosses, the highest British award for valour – but they gave way in the face of his persistence and public acclaim.

The Zeebrugge operation was a bold and ambitious concept that was conducted with enormous determination and courage. There were significant weaknesses in the planning, however: too much improvisation, insufficient attention to important details and perhaps not enough questioning of optimistic assumptions. It seemed to rest on Keyes’s tendency to assume that enthusiasm alone could overcome any difficulty. Nevertheless, even if its military impact was slight, the timely and considerable boost it provided to morale was of great value.