Los Negros and Manus form the twin hooks that enclose Seeadler Harbor. The reef-fringed entrance opens to the north. Inside, the water reaches 114 feet in places - deep enough for a battleship to swing on an anchor chain, shallow enough that dropped things can sometimes be found. The Germans recognized the anchorage's potential but never built much before their colony collapsed at the end of the First World War. Between the wars, the Australians administered the islands with a light hand. Then in 1942 Japanese forces took the Admiralties as part of their push through the Bismarck Archipelago, and the harbor became an objective worth planning an invasion around.

On February 29, 1944, General Douglas MacArthur launched Operation Brewer - a bold reconnaissance-in-force that became a full assault when the initial landings found less resistance than intelligence had predicted. American forces pushed ashore on Los Negros, then across to Manus itself. By March 19 the islands were secured. MacArthur's plan had skipped over larger Japanese garrisons further east, isolating them by seizing the chain's best harbor. Within weeks the Seabees were at work - the 46th Naval Construction Battalion among them - building piers, workshops, an airstrip, and the supply depots that would become Manus Naval Base. Seeadler Harbor had just become the staging point for everything MacArthur would do next, from the New Guinea coast to the return to the Philippines.

By late 1944 the harbor held a small floating city. Submarine chasers and PT boats tied up alongside tenders like USS Oyster Bay. Destroyers and cruisers - USS Claxton, USS Canberra, HMAS Shropshire - queued for repairs at the massive sectional dry docks USS ABSD-2 and USS ABSD-4, each nearly 930 feet long when assembled. Seaplanes skimmed in past the reef. Liberty ships unloaded bombs, shells, drummed fuel. The photograph from September 1945 that shows the harbor in quiet is almost startling - there must have been a thousand vessels out there at wartime peak. When the Japanese reconnaissance pilot reported the two drydocks as carriers in April 1945, he was not foolish. ABSD-4 alone could lift ninety thousand tons. It looked exactly like what could carry a war across an ocean.

On the morning of November 10, 1944, USS Mount Hood lay at Berth 380 near the harbor entrance. Her holds held about 3,800 tons of ammunition, and 500-pound bombs were being loaded. Eighteen men had just left for the base post office. At 08:55 the ship exploded. The first blast threw flame above masthead height. The second, seconds later, erased the ship entirely. Where she had floated, a trench on the seabed remained - five hundred feet long, fifty feet deep. Four hundred thirty-two men died. Only the eighteen ashore survived. Twenty-two nearby craft were sunk or severely damaged. The repair ship USS Mindanao, lying broadside to the blast, lost eighty-two of her own crew. Of Mount Hood's crew, one man was positively identified - and only because he happened to be aboard Mindanao at the moment of the explosion. The official investigation could never determine the initial cause.

The war ended and the harbor emptied. Ships that had been repaired here returned home; ships that could not be moved stayed. USS ABSD-4 was left at Lombrum Point after the war, officially struck from the Navy register in 1989 but already partly sunk for decades. Today, her outer walls still break the surface. Divers find Japanese wrecks in the deeper water, American landing craft on the bottom, the scar on the seabed where Mount Hood used to be. The Admiralty Islanders - who had been bystanders to all of this - inherited an anchorage full of iron. In the decades since, Seeadler has supported fishing, a PNG naval facility at Lombrum, occasional cruise ships. The name still means sea eagle. The harbor still waits, as it did for the Germans, for the Japanese, and for MacArthur, for whoever needs deep protected water next.