Outside shipping circles, however, nothing about this convoy was known at that time. Yet May 20th, the date when it reached England safely, marked one of the great turning-points of the war. That critical voyage meant nothing less than that the Allies had found the way of defeating the German submarine. The world might still clamour for a specific "invention" that would destroy all the submarines overnight, or it might demand that the Allies should block them in their bases, or suggest that they might do any number of impossible things, but the naval chiefs of the Allies discovered, on May 20, 1917, that they could defeat the German campaign even without these rather uncertain aids. The submarine danger was by no means ended when this first convoy arrived; many anxious months still lay ahead of us; other means would have to be devised that would supplement the convoy; yet the all-important fact was that the Allied chiefs now realized, for the first time, that the problem was not an insoluble one; and that, with hard work and infinite patience, they could keep open the communications that were essential to victory. The arrival of these weather-beaten ships thus brought the assurance that the armies and the civilian populations could be supplied with food and materials, and that the seas could be kept open for the transportation of American troops to France. In fine, it meant that the Allies could win the war.
On May 21st the British Admiralty, which this experimental convoy had entirely converted, voted to adopt the convoy system for all merchant shipping. Not long afterward the second convoy arrived safely from Hampton Roads, and then other convoys began to put in from Scandinavian ports. On July 21st I was able definitely to report to Washington that "the success of the convoys so far brought in shows that the system will defeat the submarine campaign if applied generally and in time."