It was not until the revolution made its next step forward by the changes in personnel announced in January that marked progress was shown in the other fields of naval war. The late autumn had been marked, as it was fully expected, once the submarine was thwarted, by various efforts on the part of the enemy to assert himself by other means at sea. A Lerwick convoy, very inadequately protected, was raided by fast and powerful enemy cruisers, and many ships sunk in circumstances of extraordinary barbarity. The destroyers protecting them sacrificed themselves with fruitless gallantry. There were ravages on the coast as well. Both things pointed to salient weaknesses in the naval position. At the time of the third naval crisis at the end of 1916, it had been pointed out that the repeated evidences of our inability to hold the enemy in the Narrow Seas ought not to be allowed to pass uncensured or unremedied. But the fatal habit of refusing to recognize that an old favourite had failed prevented any reform for a year. It was not until Sir Roger Keyes was appointed to the Dover Command and a new atmosphere was created that remarkable departures in new policy were inaugurated. This policy took two forms. First, there was the establishment of a mine barrage from coast to coast across the Channel, and simultaneously with this, North Sea minefields stretching, one from Norwegian territorial waters almost to the Scottish foreshore, and another in the Kattegat, to intercept such German U-boats as base their activities upon the enemy’s Baltic force. Two great minefields on such a scale as this are works of time. Nor can their effect upon the submarine campaign be expected to be seen until they are very near completion; but then the effect may possibly be immediate and overwhelming.