British lay mines off the Belgian coast

At the beginning of October 1914 the British Royal Navy laid a minefield in open waters for the first time in this war. The mines barred the southern edge of the North Sea, east of the Goodwin Sands off the coast of Kent, towards the Belgian coast. Britain, which since August had accused the Germans of laying mines in the open sea, thus took up the same weapon, although unlike them it publicly announced which area was mined.

A response to German mines and submarines

The Germans had been laying mines in the open sea from the first hours of the war. As early as 6 August the cruiser HMS Amphion sank on a field laid by the minelayer Königin Luise. German submarines proved an even greater threat. On 22 September U-9 sank three British armoured cruisers off the Dutch coast. The British feared that U-boats would break into the Strait of Dover and attack the transports carrying troops and supplies to France, and soon to Belgium as well.

On 2 October the Foreign Secretary, Edward Grey, instructed the British ambassador in Washington to inform the United States government that the German policy of minelaying and the activities of submarines had forced the Admiralty to take countermeasures. The area between latitudes 51°15′ and 51°40′ north and longitudes 1°35′ and 3° east was declared dangerous, a belt of sea from around the Goodwin Sands almost to the latitude of Ostend. According to some sources, on 3 October the Admiralty announced this warning publicly so that neutral ships could avoid the mined area.

A barrier on the flank of the Channel route

The mines were laid by old cruisers converted before the war into minelayers. According to British accounts, four such ships laid a barrier of 1,064 mines at the beginning of October. It was not meant to close the strait, but to shield from the north the route used by transports crossing the English Channel against submarines and surface ships.

The effectiveness of the first British minefields was doubtful. The Royal Navy’s mines of 1914 had defective sinkers and mooring cables, so many of them soon broke loose and drifted with the current, posing a danger to British ships too. One of the Admiralty officers responsible for mining equipment wrote at the time that since the sinkers and moorings of the mines were useless, the whole operation was bound to fail. Even so, it was the beginning of a great British mine war, which in the following years extended to the Strait of Dover, the Heligoland Bight and the northern exit from the North Sea. As early as 2 November 1914 Britain declared the whole North Sea a military area.