Due to the significant strategic advantages conferred by the Belgian ports, the Imperial German Navy had used Ostend as a base for the U-boat campaign during the Battle of the Atlantic since 1915.

As it was 6 mi (5.2 nmi; 9.7 km) inland, it was immune to most naval artillery fire and coastal raids, providing a safe harbour for training and repair.

When they did discover the entrance, German resistance proved too strong for the operation to be completed as originally planned: the obsolete cruiser HMS Vindictive was sunk, but only partially blocked the channel.

After the German Army captured much of Belgium following the Battle of the Frontiers in 1914, the Allied forces were left holding a thin strip of coastline to the west of the Yser.

[2] Bruges was therefore a vital asset in the German navy's increasingly desperate struggle to prevent Britain from receiving food and matériel from the rest of the world.

As British forces on the southeast coast of Britain regrouped, remanned and repaired following heavy losses at Zeebrugge, Keyes planned a return to Ostend with the intention of blocking the canal and consequently severing Bruges from the sea, closing the harbour and trapping the 18 U-boats and 25 destroyers present for months to come.

Weather dependent, under cover of a smoke screen, aerial bombardment and offshore artillery, the blockships would steam directly into the channel, turn sideways and scuttle themselves.

This operation was to thoroughly block the channel, and—coupled with the blockage at Zeebrugge (which the British authorities believed to be fully closed)—was to prevent use of Bruges by German raiding craft for months to come.

[citation needed] Torpedoes fired from motor launches demolished machine gun posts on the ends of the piers marking the canal, beginning the attack.

[13] Ten heavy bombers of the newly formed Royal Air Force then dropped incendiary bombs on German positions, but did not cause significant damage.

[16] In preparation for the attack, Godsal and Lynes had carefully consulted available charts of Ostend following the previous operation's failure caused by German repositioning of navigation buoys.

As he searched, two German torpedo boats sailed from Ostend to intercept the cruiser, but in the heavy fog they collided and, disabled, limped back to shore.

[20][21] Most of the bridge crew were killed or wounded by the blast, including First Lieutenant Victor Crutchley, who staggered to the wheel and attempted to force the ship to make the full turn into the channel.

[9] As Engineer-Lieutenant William Bury prepared to detonate the scuttling charges, Crutchley took a survey of the ship and ordered all survivors to take to the boats on the seaward side of the wreck.

Despite her sheltered position behind the cruiser, fire from shore continued to enfilade the launch and a number of those aboard, including Lieutenant Bury, suffered broken ankles as they jumped onto the heaving deck.

[24] ML254 then began slowly to leave the harbour mouth, carrying 38 survivors of Vindictive's 55 crewmen huddled on deck, where they remained exposed to machine gun fire from the shore.

As Drummond turned his boat seawards and proceeded back to the offshore squadron that was still engaged in an artillery duel with the German defenders, one of the missing launches, ML276 passed her, having caught up with the lost cruiser at this late stage.

Despite heavy machine gun and artillery fire, Bourke returned to the scene of the wreck four times before they discovered two sailors and Vindictive's badly wounded navigation officer Sir John Alleyne clinging to an upturned boat.

[22] Hauling the men aboard, Bourke turned for the safety of the open sea, but as he did, two 6 in (150 mm) shells struck the launch, smashing the lifeboat and destroying the compressed air tanks.

[22] Offshore, as Warwick's officers, Keyes' staff and the survivors of Vindictive gathered on the destroyer's deck to discuss the operation, an enormous explosion rocked the ship causing her to list severely.