Stretching across the North Sea, from Norway almost to the Orkneys, this heavy barrier of powerful mines opposed any enemy vessels which attempted to make their way around the north of Scotland into the Atlantic. The Germans had only two exits from the North Sea, the one covered by this mine barrier, and, to the south, the narrow Straits of Dover, also partially mined and guarded by the famous Dover Patrol. It was a new factor in war, this vast barrage, the most successful innovation, the biggest new naval offensive put forth after our entrance into the war. American in conception, it was also mainly American in construction. A joint British and American undertaking, as it was, four-fifths of the mines laid were of American design and manufacture, made in this country, taken across the Atlantic in American ships, and laid by American naval vessels. Though not actually laid until the summer of 1918, this was the first big project proposed by the United States Navy after our entrance into the war. In fact, it was only nine days after war was declared that the Bureau of Ordnance presented an elaborate memorandum, outlining the proposition. But the British Admiralty, without whose consent and coöperation it could not be constructed, and Admiral Sims pronounced it "impractical" and "unfeasible." It was not until six months later that we secured the Admiralty's approval, and the great project got under way. The first mine was laid on June 8, 1918. "The barrier began to take toll of the enemy's submarines as early as July 9, when one was disabled on the barrier and compelled to return to Germany," reported Admiral Joseph Strauss, commander of American mining operations in the North Sea. "It is not known how many submarines were sunk or disabled in the mine field. It has been placed as high as twenty-three. My own estimate, based on known sinkings, is ten, although I am inclined to think that is a modest one." Captain Reginald R. Belknap, commander of Mine Squadron 1, says the barrage began to yield results before it was half way across. "From the nature of the case it may never be known definitely how many actually did come to grief there," he said; "but the best information gives a probable ten before the middle of October, with a final total of seventeen or more. In addition to this toll, the squadron should be given credit for two submarines lost in the field of British mines laid by the _Baltimore_ off the Irish coast." Eight and one-half per cent of the total number of submarines lost during the war were brought into the list of missing by the barrage, was the estimate of Admiral Ralph Earle, Chief of the Bureau of Ordnance, under whose administration and leadership the mine barrage was conceived, projected and constructed. Admiral Earle reported to me: