Sinking of the San Diego

At about 11.05 a.m. on 19 July 1918 the American armoured cruiser San Diego was zigzagging off the south shore of Long Island, a dozen or so kilometres from Fire Island, when a powerful explosion occurred under her port side, near the engine room. Water flooded into the engine room and the adjacent boiler room, because a buckled bulkhead prevented the watertight doors from being closed. The ship listed to port and after about 28 minutes capsized and sank. Six sailors were killed. The rest of the crew, more than 1,100 men according to American studies, were saved. The San Diego was the only major warship the United States lost during the First World War.

The cruiser had been launched in 1904 in San Francisco as the California. She displaced about 13,700 tons and carried four 203 mm (8-inch) guns. For years she served in the Pacific, and in 1914 she was renamed San Diego to free the name California for a new battleship. After the United States entered the war in April 1917 she moved to the Atlantic. From bases in New York and Halifax (PL) she escorted convoys (PL) of troops and supplies on the first leg of the voyage to Europe, before ocean escort ships took them over. On 18 July she left the navy yard at Portsmouth for New York to take over the escort of another convoy to France.

The ship’s commanding officer, Captain Harley H. Christy, was convinced that the San Diego had been torpedoed by a submarine. He ordered general quarters and fire at anything that looked like a periscope. The gunners opened fire. The wireless was not working, so Christy sent a boat ashore for help. When the ship began to capsize, he ordered her abandoned. The crew left the deck efficiently and in good order, and Christy was the last to leave the ship. The survivors were picked up by passing ships, and several boats reached the shore of Long Island. Two sailors were killed by the explosion, one went missing by the propeller shaft, one was killed by a funnel breaking away, another by a falling life raft, and the last drowned trapped in the crow’s nest.

No one had seen a periscope or a torpedo track. Several moored naval mines were, however, found in the area, and in August a navy court of inquiry concluded that the cruiser had struck a mine. The mines had been laid by the German U-cruiser U-156 under Kapitänleutnant Richard Feldt, the same boat that in December 1917, still under another commander, had shelled Funchal. She had sailed in mid-June with orders to lay mines on the route into New York harbour, by the Fire Island lightship. Earlier still, at the turn of May and June, American waters had been visited by another large submarine, U-151, which sank many ships off the coast from New Jersey to Virginia. Other versions later appeared as well, among them that the cruiser had been blown up by a German agent. Surveys of the wreck carried out by the US Navy in 2018, however, confirmed that the damage corresponded to a mine explosion.

The sinking of the San Diego caused alarm along the whole East Coast. Naval airmen from Long Island even bombed the wreck lying on the seabed, taking it for a lurking submarine. U-156 meanwhile sailed on north. On 21 July off Orleans on Cape Cod she shelled a tug and barges, and a few shells fell on the beach. It was the only time during this war that enemy shells fell on the continental territory of the United States.