By July 1945, the Imperial Japanese Navy had effectively ceased to exist as a fighting fleet. The Combined Fleet's battleships and carriers were sunk or immobilized. But Japan's coastal waters still carried traffic -- small convoys of freighters and escorts hugging the shoreline, moving supplies between ports under cover of darkness. Halsey's Third Fleet had been ranging along the Japanese coast, its carrier aircraft striking airfields and industrial targets while the surface ships maintained a distant blockade. On July 20, Destroyer Squadron 61 received orders to break away from screening duty and conduct something far more audacious: a nighttime surface sweep into Sagami Bay, the broad indentation on the Pacific side of the Boso Peninsula that opens directly into Tokyo Bay. It was the first American surface incursion into the outer approaches of the Japanese capital since before the war.

The nine destroyers -- De Haven, Mansfield, Lyman K. Swenson, Collett, Maddox, Blue, Taussig, Samuel N. Moore, and Brush -- formed up in column, maintaining 500-yard spacing within their two divisions and 3,000 yards between divisions. They pushed through the darkness at 27 knots. At 2305 on July 22, radar operators picked up contacts at 33,000 yards. Within 15 minutes the blips resolved into a small convoy: two freighters escorted by subchaser No. 42 and minesweeper No. 1. The destroyers adjusted course to close the range. At 2351, with targets at 11,000 yards, the order came to launch torpedoes. Two minutes later, the guns opened up.

Between 2353 and 0009, the nine destroyers fired 3,291 rounds of five-inch ammunition and launched 18 torpedoes at the convoy. Two torpedoes struck home. The freighter No. 5 Hakutetsu Maru, a vessel of approximately 800 tons, was sunk. The larger Enbun Maru, at 6,919 tons, took heavy damage but survived. After-action reports claimed two ships sunk, one probably sunk, and one heavily damaged -- an optimistic assessment typical of nighttime engagements where smoke, fire, and radar returns made damage assessment difficult. The Japanese escorts, subchaser No. 42 and minesweeper No. 1, were not hit. The Enbun Maru and her escorts withdrew to Tateyama Bay. No American ship was damaged. The entire action lasted 16 minutes.

The sweep of Sagami Bay holds a particular distinction in naval history: it was the last surface action of World War II. Within three weeks, atomic bombs would fall on Hiroshima and Nagasaki, and Japan would announce its surrender. The great surface engagements that had defined the Pacific war -- Midway, the Philippine Sea, Leyte Gulf, Surigao Strait -- were already history. What remained was this: nine destroyers firing into the dark off the Boso Peninsula, sinking a single freighter in home waters that the Imperial Navy could no longer defend. The action demonstrated the totality of American naval dominance in the war's final weeks. Halsey's destroyers could now enter the approaches to Tokyo Bay itself, operate at will, and withdraw without loss. The crew of the USS Samuel N. Moore later compiled their experiences into a book titled Our Ship's Diary As Told By The Crew, one of the few firsthand accounts of this brief, terminal engagement.