Then, after getting underway for Belgium on the 29th, she reached Brussels late on 2 July and there received her only royal visit when, on the morning of the 8th, King Leopold III and Queen Astrid came on board for an hour's inspection.

Following brief operations off Pyramid Cove, San Clemente Island, Aylwin sailed for the Canal Zone on 27 April to participate in Fleet Problem XVII, a five-phased evolution.

Rated as "damaged" in an initial phase of the action on 8 May, Aylwin shaped course to rendezvous with "friendly" units that morning and drove off two "strafing" attacks by "Black" planes en route.

The beleaguered ship found no solace en route, however, for she spotted three fast minelayers closing from six miles away, and after identifying them as "enemy", went to general quarters at 07:30, "opening fire" three minutes later.

For the rest of 1937 and the winter months of early 1938, Aylwin maintained what had become standard routine, alternating periods in port for upkeep with time training at sea in the southern California operating area.

The forces then all retired to Culebra Bay, Puerto Rico, where President Franklin D. Roosevelt reviewed them from the deck of Houston on the last day of February.

She planeguarded for USS Yorktown en route to Panama; transited the Canal on 29 April; and, after tarrying briefly at Balboa, got underway for San Diego on 2 May.

Reaching her home port on the 12th, the destroyer operated off southern California before entering the Mare Island Navy Yard on 18 June for repairs and alterations lasting until 8 October.

Indicative of the Fleet's security-mindedness at that time, Aylwin alternated with other destroyers conducting "security patrols" off the port of Honolulu and off Pearl Harbor's entrance during the course of the evolutions, investigating all vessels sighted, including small fishing craft.

Aylwin thus returned briefly to the west coast during the summer of 1940, reaching San Diego on 9 July before shifting to the Mare Island Navy Yard on the 14th.

On 7 February 1941, she put to sea and, after rendezvousing with aircraft carrier Enterprise and sister destroyer USS Farragut, headed back to the west coast for a brief visit.

As Aylwin lay moored in a nest with her squadron mates on the morning of 7 December 1941, one small boiler was in operation to provide enough power for auxiliary services on board.

The destroyer, manned by 50% of her crew under the direction of four ensigns—the senior officer, Ensign Stanley B. Caplan, USNR, had served at sea for only some eight months—proceeded out of Pearl Harbor, stripping ship for war and simultaneously maintaining a "continuous fire."

Nevertheless, in view of ComDesRon 1's instructions, Aylwin could not slow down, but instead headed out to sea for patrol duty, leaving most of her officers orphans on board the old flushdecker USS Chew.

Rodgers heaped praise on his abbreviated crew for their actions in the first flush of war: "The conduct of the personnel was magnificent.... Every man more than did his job and was eager to fight."

Of Ensign Caplan, Rodgers wrote, "The conduct (of this man) ... in superbly taking command for 36 hours during war operations of the severest type is a most amazing and outstanding achievement."

After investigating several suspected submarine contacts en route, Aylwin covered the arrival of TF 11 at Pearl Harbor three days after Christmas.

Aylwin then underwent repairs and alterations in the Mare Island Navy Yard until 10 January, receiving new 20-millimeter machine guns to increase her close-in antiaircraft capability.

On the last day of January, the destroyer sortied with TF 11, formed around Lexington, and performed plane-guard duties for that carrier as she moved southwestward toward New Guinea.

After accidentally firing a live torpedo in Hull's direction during surface attack maneuvers on 13 February, Aylwin warned her sister ship by blinker, enabling the latter to sheer away out of danger.

While alongside New Orleans to refuel two days later, Aylwin rigged breeches buoys forward and aft, and took on board 37 officers and 92 enlisted men from Lexington and one Yorktown pilot, Lt.

Less than an hour later, while the carrier's planes flew protective cover, TF 17 entered Nukualofa Harbor, Tongatapu, where Aylwin transferred her passengers to Portland while fueling from the heavy cruiser.

The following day, 28 May, Aylwin got underway to sortie in the screen of Enterprise and USS Hornet as those carriers proceeded to waters north of Midway await a Japanese armada.

Aylwin completed her post-repair trials and then departed Pearl Harbor on 2 August to screen the escort carrier USS Long Island which had embarked the marine air units earmarked to operate from the airfield on Guadalcanal after its capture.

That news, combined with the withdrawal of the three carriers supporting Operation Watchtower, prompted orders on the 10th for Aylwin and her charge to put into Suva, Fiji, to fuel and there await further instructions.

After protecting that seaplane tender, four days later, she escorted Ballard to Vanua Levu to pick up sick Army coastwatchers before returning to Espiritu Santo for fuel from the oiler USS Tappahannock.

Following repairs at Alameda, California, Aylwin picked up a convoy of tank landing ships and motor minesweepers at San Diego to escort to Hawaii.

But for a run to Majuro and back between 8 and 11 February, she served there until shifting to Eniwetok on the 21st to join USS Hall, MacDonough, and Monaghan in delivering fire support that night on Parry Island.

On 30 March, the Fast Carrier Task Force commenced intensive bombing of Japanese airfields, shipping, fleet servicing facilities, and other installations in the Carolines, continuing the raids until 1 April.

Aylwin helped to drive off planes during the approach of the carriers on the 29th and 30th and, at 13:43 on the latter day, sighted a damaged Curtiss SB2C "Helldiver" from Bunker Hill's air group ditch a short way off.