ALTHOUGH the convoy system was employed at the beginning of the war for the transport of the Imperial armies to France, and subsequently for all the Allied troop movements overseas, it was some three years later before it was extended to the entire British Mercantile navy, on which the United Kingdom depended for too many of the necessities of civilised life. The rapid development of submarine piracy, however, compelled the Admiralty, early in the year 1917, to resort to what was merely a new form of the old system of protecting sea-borne trade. This comprised the collection of all merchant ships passing through the danger zones into nondescript fleets, and the provision of light cruisers, destroyers, torpedo-boats, trawlers and occasionally (for coastal convoys) of patrol launches to escort them. Certain types of aircraft were also frequently used for observation and scouting purposes. Previous to the adoption of the convoy system a merchantman, whether it was a fast-moving liner or a sturdy but slow ocean tramp, _zigzagged_ through the danger zones with lights out and life-boats ready. Many were the exciting runs made in this way, with shells ploughing up the water around and torpedoes avoided only by the quick use of the helm; but the courage of our merchant seamen was of that indomitable character exhibited now for over three centuries, since the days of Drake, Hawkins, Raleigh and the other sea-dogs of old. But the danger zones grew wider as the radius of action of newer and larger German submarines increased. At last no waters were immune, from the Arctic circle to the Equator, or from Heligoland to New York. The hour was one of extreme peril for the sea-divided Empire. To lose several hundred ships, with many thousands of lives and much-needed cargoes of food and munitions, when the valiant armies of civilisation were battling with the Teuton hordes, was bad enough; but if the enemy had been able, by casting aside the laws of humanity and sea war, to compel British ships to remain in harbour or meet certain destruction on the high seas, the result could only have been the complete failure of the Allied cause, the conquest of Europe and the fall of the greatest political edifice since Imperial Rome. Between the world and these catastrophes, however, stood the undefeated Mercantile Marine and the Allied navies. Councils were held in the historic rooms of Whitehall and the old convoy system emerged from the archives of Nelson's day. The commerce raiders were no longer the canvas-pressed privateers of the sixteenth, seventeenth and early eighteenth centuries, who fought a clean fight, often against great odds, but were submarine pirates of the mechanical age, who only appeared from the sea depths when their victims had been placed _hors de combat_.