By February 1943, examples of the new Chance Vought F4U Corsair had arrived with VMF-124. Although the squadron's first missions were not as successful as hoped, the big, gull-winged fighter soon became the mainstay of the shore-based Marine Corps fighter organization, quickly supplanting the veteran Wildcat.  The first Corsair-mounted Marine ace was 1st Lieutenant Kenneth A. Walsh, a former enlisted pilot.

Deliveries of the F4U to VMF-124 started in October, 1942, when the squadron was still stateside. The planes needed a lot of refinements and the pilots needed a lot of training in them.  But after a few short flights in the Corsairs, they were sent to the Pacific, where they were badly needed to carry out escort missions that the Wildcats couldn't handle, because of their limited range and combat capability.  Only Corsairs and P-38 could provide the long-range escort required.  VMF-124's twenty-four Corsairs went to Espiritu Santo in the jeep carrier Kitty Hawk in January, 1943.  The pilots caught up with the planes and flew up to Guadalcanal on February 12.  They had already been assigned a mission for that same day!  The mission was to escort a PBY Catalina which was going to rescue a couple Wildcat pilots off Kolomabangara, Jefferson DeBlanc and James Feliton, who had ditched earlier and were now in the care of coast-watchers on Vella Lavella.  The Catalina also made an unplanned stop to pick up an Army P-38 pilot who had ditched off New Georgia, only 50 miles from a large Jap Zero base.  But the newly-arrived pilots of VMF-124 finished their escort mission without incident, some pilots having logged nine hours flight time that day.

While Ken Walsh and the other fliers of VMF-124 had hoped for some time to familiarize themselves with the area, the islands, and the locations of enemy troops. But the next day they were escorting B-24s to Bougainville, 300 miles up The Slot.  On this mission Lt. Walsh led the third four-plane element (group of 4), thus he was number 13.  He was not superstitious and the number stuck; he usually flew number 13 thereafter.  The flying continued on the following day (February 14), Walsh's first exposure to actual combat.  Again, they were escorting B-24 bombers, this time to Kahili airdrome on Bougainville, but the Zeros were ready for them, having been warned by the Japanese' own coast-watchers. 

The Americans lost eight planes, the Japs three, in what was inevitably called "The Saint Valentine's Day Massacre." As one of the first Cosair squadrons, the pilots of VMF-124 were anxious to establish a tactical doctrine for the Corsairs that later squadrons could build on.  When they asked one of the early, well-known, high-scoring Wildcat pilots about how to approach combat with the Japanese, they were told "you've gotta go after 'em."  Walsh quickly learned the importance of altitude, as this was one of the Corsair's key advantages over the Zero.  He also learned to avoid slow speed dogfights, because of the Zero's superior manoeuvrability at speeds below 300 mph.

His first kill came on April 1, 1943, on patrol over the Russells.  The Marine F4Us circled their assigned area quietly for two hours, then were relieved by some P-38s, which were promptly jumped.  Walsh alerted his flight and turned them back from their homeward course to help the Lightnings.  As a wild melee was taking place, the Zeros didn't notice the Corsairs in time.  Walsh lined one up for a deflection shot and missed, but his wingman scored, burning up the Zero.  They came undetected upon a second Zero, and Walsh hit and destroyed him.

He gained three more kills on May 13.

By mid-August, he had doubled his score to 10, when VMF-124 moved over to the newly captured airbase at Munda.  On the 12th, Walsh's wingman, Lt. Johnston,  saved his life by getting a Zero off Walsh's tail.  Walsh had been badly shot up, his plane was on fire, and the Zero was about to finish him off when Johnston flicked him off.  Walsh managed to get back to an emergency strip at Segi, New Georgia, but landing without much control, he smashed into another Corsair on the line.  Both planes were lost.  It makes one wonder if the Jap pilot got credit for two kills that day.

On the 15th, Walsh was flying CAP over the invasion beaches at Vella Lavella, when the fighter director warned of bogeys coming in.  Some Zeros and Vals came in, and Walsh shot down two, before a Zero clobbered him, hitting his starboard wing tank.  The plane could still fly, and Walsh headed for home, only to suffer an attack of vertigo and looping wildly.  He was able to recover control and land safely, but the plane was scrapped and used for spares.  One wing was all shot up, and they didn't have facilities in the field to change wings.  But they felt they had accomplished their mission in turning back the Vals from the landing zone.

On August 30, Walsh fought an incredible battle against 50 Japanese aircraft, shooting down four enemy fighters before he had to ditch his damaged Corsair. Assigned to escort bombers headed for Jap bases on Bougainville, his plane soon developed engine problems. He landed at an advanced base at Munda, and immediately secured a replacement Corsair. He continued on, now alone, but hoping to catch up with his squadron. From his isolated vantage point, he attacked a gaggle of Zeros that were going after the B-24s, shooting two of them down. On the return he picked up a message from other B-24s, in trouble over Gizo. He flew off to help, and again downed two Zeros. But one of the Japs damaged Walsh's Corsair, and he was forced to ditch off Vella Lavella. It was his third water landing in six months.

He was awarded the Medal of Honour for this mission.

He ultimately scored 21 kills, of which 17 were Zeros.  He lost five aircraft: three times shot down and the two noted above on August 15.  His first combat tour in the Solomons lasted seven months, from February to September, 1943.  He returned for a second tour with VMF-222 later in the war, flying the advanced F4U-4.  He scored his last victory on June 22, 1945, downing a kamikaze Zero over northern Okinawa.