These activities were overshadowed at the time by graver events, or hidden by military secrecy. Few people even today know that ships were sunk and men killed by German U-boats within sight of our coast.[1]
It was in no sense an all-out effort. Only a handful of submarines were used. The attack was launched late in the war, in fact one of the six didn’t even reach American waters, was called back by news of the Armistice. Submarines of that day had a cruising range of some three months, could spend only three weeks in our coastal waters, used the rest of the time getting over and back.
But in those few weeks these six submarines destroyed exactly 100 ships, of all sizes, types and registry, killed 435 people. Most of the ships were peaceful unarmed merchantmen, coastwise ships from the West Indies and South America, tankers from Galveston, fishing ships heading back from the Grand Banks, supply ships carrying guns and war materials to England, a few stragglers from convoys.
The subs’ biggest catch was the USS San Diego, a cruiser, sunk by mine off Fire Island, just outside New York harbor, July 19, 1918, with 1,180 officers and men aboard. Only six lives, fortunately, were lost. The battleship Minnesota, escorted by a destroyer, struck a mine off Fenwick shoals light ship, early in the morning of September 29, but made temporary repairs and limped back into Philadelphia Navy Yard 18 hours later. A fragment of the mine was found imbedded in her frame work.
Reproduced from U.S. Navy map showing track of submarines operating in American waters during last few months of first World War.
Mines were laid at strategic points. One field, with its mines 500 to 1,000 yards apart was laid off Cape Hatteras, one at the mouth of Chesapeake Bay, one across Delaware Bay, two in between these key inlets, another off Barnegat, and the last off Fire Island. Some of the mines drifted ashore, others were found and destroyed—the last ones not till the following January. But mines accounted for six of the ships lost.
One of the submarines, the U-117, built as a mine layer, planted 46 of the 58 mines laid along our shores; four others were merchant subs of the Deutschland type, including the Deutschland itself, which had twice previously visited this country on ostensibly friendly missions.
Though the subs encountered a few victims on the way over or back, most of the ships were destroyed in the shallower waters within 200 miles of the American and Canadian coast. The fishing was better close in.
Naval Intelligence knew, through Admiral Sims’ office in London, just when each submarine left Kiel, what its probable destination was, and its approximate arrival date. The Navy could not broadcast this information, lest U-boat captains learn they were expected, but took appropriate defense measures. Even so, each submarine traveled directly to its destination, carried out its mission.