Mine barrage off the Belgian coast

On 24 April 1916, Easter Monday, British ships laid off the coast of occupied Belgium a barrage of mines and mine nets nearly 30 kilometres long. It was meant to hamper the sorties of the submarines of the German Flanders Flotilla from Zeebrugge and Ostend, which for months had been sinking ships and laying mines on the approaches to Dover, the Thames and the French ports. The operation was planned and led by the commander of the Dover Patrol, Admiral Reginald Bacon.

Bacon’s plan

Bacon took command at Dover in April 1915, when the barrage in the Strait of Dover had closed that route to the large U-boats from Germany. The first British minefields off the Belgian coast had been laid as early as the autumn of 1914, but the small UB and UC-type submarines, the first of which were carried from Germany by rail and assembled in Antwerp, left the Flanders ports without much hindrance. In the spring of 1916 they became particularly dangerous. It was a boat of the Flanders Flotilla that in March torpedoed the Sussex. Bacon therefore proposed to fence off from the seaward side a belt of water off Zeebrugge and Ostend, in which British monitors and destroyers could patrol constantly without fear of attack from under water. The boundary of this belt was to be formed by mine nets, that is, nets with mines hung on them that exploded when a submarine became entangled, reinforced by ordinary mines laid deep.

24 April

On the afternoon of 23 April four minelayers under Commander F. S. Litchfield-Speer left the Thames estuary escorted by destroyers from Harwich. By four in the morning on 24 April they were in position, and by 7.30 they had laid a double line of mines about 15 nautical miles (almost 28 kilometres) long, from the shoals in the west to the waters near the Dutch border. Behind them came Trinity House vessels laying large light buoys to mark the line, and divisions of drifters, fishing boats taken into the navy, which paid out the mine nets. By evening more than 13 miles of them had been laid. The whole operation was covered by two monitors, destroyers from Harwich and Dunkirk, and French destroyers.

The Germans quickly noticed what was happening. German seaplanes appeared over the barrage, one of which was shot down. A German coastal battery shelled the monitor General Wolfe from a range of almost 30 kilometres. In the afternoon three German destroyers came out of Zeebrugge. Four British destroyers went after them, but came too close to the shore and fell under the fire of the batteries. A shell pierced the engine room of the destroyer Melpomene, and the others were hit too. The ships had to withdraw, covered by the fire of the monitors. The drifter Clover Bank lost her bearings, ran onto the freshly laid mines and blew up. According to Bacon, the British lost one officer and 17 seamen that day, most of them from Clover Bank. The outermost mines were laid by mistake in Dutch waters, and two Dutch torpedo boats came to protest.

In the evening the Admiralty ordered Bacon to break off the operation and recall his ships, because the German fleet had put to sea; the next morning it bombarded Lowestoft. The work was completed in the following days. By 7 May the whole net barrage was ready.

Consequences

The British were convinced that they had destroyed several submarines on the very first day. The drifter crews reported that two U-boats had become entangled in the nets and had been finished off with bombs, and further explosions were heard in the minefield. Bacon wrote of four, perhaps five boats sunk. In reality the Germans most probably lost only one boat that day, UB-13, the same one that in March had sunk the Dutch liner Tubantia. She left Zeebrugge on the evening of 23 April and was lost with all hands. According to some researchers it was she that became entangled in the net of the drifter Gleaner of the Sea; according to others she may have been lost on one of the mines.

Patrols along the barrage line, repairs to the nets and skirmishes with German destroyers continued until 10 October 1916. Bacon later claimed that for five months the barrage had completely stopped German minelaying in the waters off Dover. The submarines from Flanders did not stop putting to sea, however, and the Strait of Dover was sealed effectively only at the turn of 1917 and 1918.