Following the unsuccessful attack on Zeebrugge on 12 May, Vice-Admiral Bacon turned his attention to the dockyard at Ostende, a larger target, but one that was flanked by houses.
After the weather curtailed a number of early attempts on 26 and 27 May, the HMS Erebus and HMS Terror, with destroyers and auxiliary craft, set out this evening.
To cover the operation in the direction of the Thornton Bank and the Schouwen Bank, Commodore Tyrwhitt went out with the Harwich Force, and, early next morning, he intercepted two German destroyers, one of which, the S.20, he sank. In the later stages of this destroyer action, German seaplanes from Zeebrugge took part and, coming down on the water, they picked up and carried home one officer and seven men of the crew of the S.20.
From 16,000 feet above Ostend, part of the destroyer action was watched from the aeroplanes which were in position ready to direct the fire of Vice-Admiral Bacon’s monitors.
There were two DH4 aeroplanes for spotting, escorted by two others and by two Sopwith Pups. In addition, to prevent German aircraft spotting for the shore batteries against the ships, or from making direct bombing attacks on them, there were two fighter patrols in the neighbourhood.
The air observer’s signal that he was ready was made at 0322 and fire was opened within a few minutes. To avoid a possible initial shelling of the town, the monitors were ranged on a point about a 1,000 yards short of the eastern boom, and the guns were not lifted on their target until the line and direction had been given as correct. When the range was lengthened, fire was at once reported on the target, and a central hit was quickly signalled. Soon after fire was opened a German kite balloon ascended 5,000 feet behind Ostend presumably to direct the enemy coast batteries on the bombarding ships. One of the patrolling pilots in a Sopwith Pup, diving from 18,000 feet, shot the balloon down. Meanwhile numerous enemy smoke screens had been started and, by 0345, the docks and the surrounding country had become obscured. The smoke spread until it covered about ten to fifteen square miles, including the entire harbour, and, at 0400, Vice-Admiral Bacon judged it was useless to continue. Of the 115 rounds fired at that point, 36 had been spotted from the air, and photographs taken later in the day showed that at least twenty shells had fallen on the docks.
One object of the bombardment, the infliction of damage on the destroyer repair shops, had been attained. It was also revealed by U-boat prisoners, taken shortly afterwards, that the bombardment led to the sinking in the harbour of the submarine UC70 as well as an armed trawler, and that three destroyers which could not get out of harbour in time were damaged. The UC70 had been lying alongside a petrol lighter which was exploded by a direct hit; the U-boat was afterwards raised and repaired at Bruges.