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.
With blimps operating from such bases, in addition to the patrols being executed by other naval craft, we might conclude that no submarine could venture within 100 miles of the American coast during daylight hours without considerable risk of detection, and that blimps should be able to make contribution to the safety of coastwise shipping and harbor cities.
The patrol areas assigned to the blimps would have their flanks exposed, but airship patrol would be co-ordinated with that of airplanes and surface craft, guarding the areas farther out.
That this conclusion is reasonable is indicated by the fact that from 1939 on, Lakehurst Naval Air Station, under command of Commander G. H. Mills had been doing just this, patroling areas all the way from Nantucket to Cape Hatteras.