The U-boat captain, one of the best in the German navy, drove his craft at a sharp angle to 400 feet. One charge exploding underneath the sub turned it stern upward till it stood almost perpendicular. He managed to level out finally at 415 feet, lay there as long as he dared, finally reached the surface. His ship was so badly crippled it had to abandon its mission and set out for home—though it sunk a couple more ships in the mid-Atlantic on the way back. The only U-boat casualty was the U-156 which after getting 34 victims in American waters, getting eight in one day, was itself sunk by mines—but off Faroe Island as it was almost home. This then is the story of submarine operations in U. S. waters in 1918—a half hearted effort of short duration started late in the day—but which destroyed 100 ships, totalling 200,000 tons, most of them close to our shores. No one could doubt but that in the event of another war submarines would be used again, and in more vigorous fashion. The American fleet might easily keep major enemy ships at a safe distance, and bombing attack from any part of Europe or over the Pacific would have little military value. But certainly submarines would find their way past the screen of Navy craft, bob up off American harbors, again to lay mines in the path of coastwise steamers, deliver hit-and-run attack by torpedo and gunfire at American craft. We could be equally sure that these ugly motorized sharks, churning the muddy sub-surface waters, would not be satisfied to attack merchantmen only, would be looking for bigger prey. On the map showing the operations of German submarines in 1918 let us superimpose, as an example, the patrol area which two blimps, basing at Boston, Lakehurst, Cape May and Norfolk might effectively cover in a 12 hour period. A patrol area of 2,000 square miles per ship is conservative. It assumes the ship flying at no faster than 35 knots, having visibility of five miles in all directions. As a matter of fact, allowing a little more than 40 knots speed—and the airship cruises considerably faster than that—we might say that a modern blimp could patrol an area 10 miles wide and 500 miles long in the 12 hours, or an area of 5,000 square miles. But by criss-crossing back and forth in accordance with a progressive plan, an area of 2,000 square miles could be made reasonably secure—except under extremely adverse conditions of visibility. Laying these patrol areas down over the map of submarine operations of 1918 it is apparent that such patrols would cover much of the territory where ship sinkings were achieved, cover all of the areas where mines were laid.