THE possession of the Belgian coast by the Germans gave them advanced bases for destroyers and submarines 300 miles nearer their objectives than the Frisian river- mouths. From Zeebrugge to Dover is only sixty-two miles, and to Dunkirk less than forty. About two submarines a day issued forth to infest the Channel. Sixteen destroyers were generally in readiness. Except in high summer the hours of darkness were always long enough to give them a wide choice of enterprises, against which it was impossible to keep concentrated anything approaching an equality of force. The enemy might raid the drifters protecting the barrage, bombard Dunkirk or Dover, attack the great mass of shipping always anchored in the Downs, where the blockade examination took place, or go north against the mouth of the Thames and the coast towns of Essex and Suffolk. He could safely fire without warning on any ship encountered with the certainty that it must be hostile. Such raids were in fact much less frequent than the Commander of the Dover Patrol apprehended as possible, though they were well organized and dashingly executed. Once only were they caught and punished, when in April 1917 Commander Evans in the destroyer-leader Broke sank two enemy boats, one by ram and the other by torpedo.
Yet this imminent cloud of danger proved very exhausting to the Dover Patrol, and if the enemy had ever broken clean into the Straits he might have sunk thousands of soldiers in passing transports. It is therefore clear that large strategical issues were involved in an attack against the Belgian coast.
Until the end of 1917, however, the Admiralty always refused to sanction an expedition, partly because of the great risk, partly because it was considered only practicable in conjunction with an advance against Bruges by