EARLY in 1917 the losses of the merchants' ships and men had assumed a proportion that called for a radical revision of the systems of naval protection. Concentrating their energies on but one specific form of sea offence, the enemy had developed their submarine arm to a high point of efficiency. Speed and power and lengthy sea-keeping qualities were attained. To all intents and purposes the U-boats had become surface destroyers with the added conveniency of being able to disappear at sight. They conducted their operations at long distance from the land and from their bases. The immense areas of the high seas offered a peculiar facility for 'cut-and-run' tactics: the system of independent sailings of the merchantmen provided them with a succession of victims, timed in a progression that allowed of solitary disposal. Notwithstanding the matured experience of submarine methods gained by masters, the rapid evolution of counter-measures by the Royal Navy, the courage and determination of all classes of seafarers, our shipping and that of our Allies and the neutral nations was being destroyed at a rate that foreshadowed disaster. Schemes of rapid ship construction were advanced, lavish expenditure incurred, plans and occupation designed--all to ensure a replacement of tonnage at a future date. More material in point of prompt effect were the efforts of the newly formed Ministry of Shipping to conserve existing tonnage by judicious and closely controlled employment. All but sternly necessary sea-traffic was eliminated: harbour work in loading and unloading was expedited: the virtues of a single control enhanced the active agency of the merchants' ships--now devoted wholly to State service. Joined to the provisional and economic measures of the bureaux, Admiralty reorganized their methods of patrol and sea-supervision of the ships. The entry of the United States into the world war provided a considerable increase of naval strength to the Allied fleets. Convoy measures, that before had been deemed impracticable, were now possible. Destroyers and sloops could be released from fleet duties and were available as escorts. American flotillas crossed the Atlantic to protect the sea-routes: Japanese war craft assisted us in the Mediterranean.