Mayaguez incident

On the early morning of 13 May, the P-3 Orions identified large radar returns near Poulo Wai and dropped flares on the suspected location of Mayaguez provoking Khmer Rouge gunfire. Low on fuel, the two Orions returned to base and were replaced with another Orion from Patrol Squadron 17. At 08:16 local time the Orion made a low pass over Poulo Wai positively identifying Mayaguez and again drawing Khmer Rouge gunfire.[7]^:50–51

Shortly afterwards the Khmer Rouge leader, Sa Mean, ordered Captain Miller to get Mayaguez under way. At 08:45 Mayaguez set off towards the northeast following one of the Swift Boats.[7]^:53 The Orion continued to track Mayaguez as it left Poulo Wai. Once the location of Mayaguez was identified, Admiral Gayler ordered the commander of the Seventh Air Force, Lieutenant General John J. Burns, at Korat Royal Thai Air Force Base, to move combat aircraft to the area.[7]^:54 At 13:00 two unarmed United States Air Force (USAF) F-111 fighter-bombers diverted from a training mission began making low-level high-speed passes by Mayaguez. Once the F-111s had left, Sa Mean ordered Captain Miller to follow the Swift Boats around Koh Tang and drop anchor approximately 1.5 km north of the island.[7]^:54–55 Two F-4 Phantoms soon arrived over Mayaguez and began firing their 20 mm cannon into the water in front of the ship. The F-4s were followed by A-7D Corsairs and more F-111s which continued to fire into the sea in front of and behind the ship indicating that no further movement should be attempted.[7]^:55–56[8]^:95

At 16:15, the Khmer Rouge ordered Mayaguez's crew onto two fishing boats which then took them closer to the shore of Koh Tang.[7]^:56–58

U.S. Navy warships Coral Sea, Harold E. Holt and Henry B. Wilson were all scheduled to arrive on station by 15 May, but none of these ships carried any troops.[7]^:61 USS Hancock carried a Marine contingent but could not arrive on station until 16 May, while USS Okinawa also carried Marines but could not arrive until 18 May.[7]^:61–62

III Marine Amphibious Force (III MAF) assigned Task Force 79.9 with recovering Mayaguez and designated D Company 1/4 Marines in the Philippines as the unit that would actually retake Mayaguez, but General Burns wanted additional force and orders were sent to the 3rd Marine Division on Okinawa. 1st Battalion, 9th Marines (BLT 1/9) was then on alert as the primary "air contingency" reaction force, but most of BLT 1/9 were ending their tours of duty and were not subject to further extension of their tours except in the case of emergency. III MAF requested the extension of BLT 1/9's tour but this was refused.[7]^:62 2nd Battalion, 9th Marines (BLT 2/9) (commanded by Lieutenant Colonel Randall W. Austin) was then in a training exercise on Okinawa and it received orders on the night of 13 May to return to camp and prepare for departure by air at dawn on 14 May.[7]^:63–65 On the morning of 14 May BLT 2/9 boarded USAF C-141s at Kadena Air Base to fly to Thailand.[7]^:66 The 9th Marine Regiment had been the first U.S. ground combat force committed to the Vietnam War in 1965, but in May 1975 only a few of the officers and non-commissioned officers from BLT 2/9 had seen combat in Vietnam.[7]^:65–66

Nine USAF HH-53C Jolly Green helicopters of the 40th Aerospace Rescue and Recovery Squadron and 10 CH-53 Knives of the 21st Special Operations Squadron stationed at Nakhon Phanom Royal Thai Navy Base were available for the rescue operation.[9]^:239 There were differences between the two types which would become relevant during the battle: the HH-53 was air-refuellable, had 450 US gallons (1,700 l; 370 imp gal) self-sealing fuel tip tanks, a tail minigun with armor plating, and two waist miniguns. The CH-53 was not air-refuellable, had 650 US gallons (2,500 l; 540 imp gal) non-self-sealing tip tanks and two waist miniguns. Thus, the HH-53's fuel tanks were less vulnerable to ground fire and with its refueling capability, could remain in the battle area indefinitely as long as it had access to an aerial tanker.[9]^:245

An aerial surveillance photo showing two Khmer Rouge Swift Boats during the initial seizing of the SS Mayaguez

On 13 May Burns and his Seventh Air Force staff developed a contingency plan to retake Mayaguez using an assault force composed of men of the USAF 56th Security Police Squadron. 75 volunteers from the 56th would be dropped onto the containers on the decks of Mayaguez on the morning of 14 May. In preparation for this assault five HH-53s and seven CH-53s were ordered to proceed to U-Tapao for staging.[7]^:76–77 At approximately 21:15, one of the 21st SOS CH-53s (68-10933, call sign Knife 13) crashed en route to U Tapao, killing 18 security police and its five-man crew.[9]^:240[10]

These 23 USAF Security Policemen were killed when their helicopter crashed due to a mechanical failure

President Ford chaired an NSC meeting at 10:22 EDT (21:22 Cambodia), where the Air Force rescue plan was cancelled due to the loss of Knife 13 and the fact that the containers on Mayaguez could not bear the weight of the helicopters while rappelling men down would expose them to gunfire.[7]^:79 It was decided that it was necessary to wait for the Navy ships to arrive off Koh Tang and for the Marines to assemble in Thailand before a rescue attempt would be mounted. President Ford ordered the Air Force to stop any Cambodian boats moving between Koh Tang and the mainland.[7]^:80

Early on the morning of 14 May, the Khmer Rouge loaded Mayaguez's crew onto one of the fishing boats and they left Koh Tang following two of the Swift Boats on a heading for Kampong Som.[7]^:91 Two F-111s swept past the fishing boat, followed by a pair of F-4s and a pair of A-7s, which began firing in front of the Swift Boats and then directly at the Swift Boats, causing one of them to turn back to Koh Tang. The jets were then joined by an AC-130H Spectre gunship from the 388th Tactical Fighter Wing which proceeded to engage the second Swift Boat with its cannons.[7]^:92 An A-7D then sprayed the Swift Boat with its 20 mm cannon, sinking it.[7]^:96 The fighters then came at the fishing boat dropping bombs and firing their cannon into the water in front of it, spraying the boat with shrapnel.[7]^:92 The fighter crews reported back that 30 to 40 Caucasians had been seen on board the fishing boat.[7]^:97

In Washington, President Ford convened another NSC meeting at 22:30 EDT (09:30 14 May Cambodia).[7]^:97 A communication link had been established between the White House, Seventh Air Force at Nakhon Phanom, CINCPAC in Hawaii and the aircraft orbiting above Koh Tang allowing for near real-time communications.[7]^:95–96 The orbiting fighters reported that they could try to shoot the rudder off the fishing boat to stop its progress to Kampong Som, but the NSC decided that the risk of killing Mayaguez crew was too great. At 23:00 EDT (10:00 Cambodia) President Ford ordered that only tear gas should be dropped on or near the fishing boat, while all patrol boats should be sunk.[7]^:97–99

The NSC meeting continued to consider the appropriate course to resolve the crisis. It was informed that the Chinese Foreign Ministry in Beijing had refused to pass on the American note intended for the Khmer Rouge, but George Bush reported that they had read the note and that it might have been relayed to the Khmer Rouge.[7]^:99 With a diplomatic solution appearing unlikely, General David Jones, acting Chairman of the Joint Chiefs of Staff, presented the NSC with a range of military options. Rescue planning was complicated by the uncertainty surrounding the location of Mayaguez's crew. It was believed that some were still on the ship, some on Koh Tang and others were on the fishing boat bound for Kampong Som. The NSC decided to proceed with a simultaneous attack by Marines to retake Mayaguez and attack Koh Tang, together with attacking Cambodian shipping and bombing mainland targets.[7]^:100

At 10:10, despite having been hit by tear gas, the fishing boat arrived at Kampong Som.[4] The Khmer Rouge commander at Kampong Som, apparently fearing attack by the Americans, refused to accept responsibility for Mayaguez's crew and so the fishing boat moved further down the coast, dropping anchor off the island of Koh Rong Sanloem. The orbiting fighters lost track of the fishing boat once it entered the port at Kampong Som, and so this was the location transmitted up the chain of command.[7]^:104–109 At 11:29, U.S. aircraft sank another patrol boat and damaged another four.[7]^:337

1/4 Marines had arrived at U-Tapao from the Philippines at 05:45 on 14 May and had been waiting on standby for a helicopter assault on Mayaguez, but as the news of the arrival of the fishing boat at Kampong Som came in the helicopter assault was cancelled.[7]^:111–112 At 14:00, BLT 2/9 began arriving at U-Tapao.[7]^:112

USAF reconnaissance photo of Koh Tang, showing East Beach and two downed CH-53s (left) and West Beach (right)

On the afternoon of 14 May, General Burns received the order to proceed with a simultaneous assault on Koh Tang and Mayaguez timed to begin just before sunrise (05:42) on 15 May.[7]^:112 D Company, 1/4 Marines would retake Mayaguez while BLT 2/9 Marines would rescue the crew on Koh Tang.[7]^:113 With minimal intelligence available regarding the geography of Koh Tang, the commander of BLT 2/9 and his staff took off in a U-21 to make an aerial reconnaissance of the island. Arriving over Koh Tang at 16:00, they were prevented from closely approaching the island in order not to compromise the secrecy of the mission or draw ground fire, but they determined that the island was so covered in jungle that the only two viable landing zones available were beaches on the west and east shores of the northern portion of Koh Tang.[7]^:114 The Defense Intelligence Agency had made an assessment, in part from RF-4C and U-2 reconnaissance flights, that between 150 and 200 Khmer Rouge backed by heavy weapons occupied Koh Tang. This report was conveyed to U-Tapao, but was never briefed to the planners, probably due to security classification issues, who believed that only about 20 Cambodian irregulars armed with small-arms were on the island.[11]

At 21:00, the rescue plan was finalized. Six hundred Marines from BLT 2/9 — composed of E and G Companies — were assigned to conduct a combat assault in five CH-53 Knives and three HH-53 Jolly Greens to seize and hold Koh Tang.[9]^:245 Two helicopters would make a diversionary assault on the West Beach (10.316°N 103.135°E / 10.316; 103.135), while six helicopters would make the main assault on the wider East Beach (10.316°N 103.139°E / 10.316; 103.139). The East Beach force would move to the nearby compound where Mayaguez's crew was believed to be held and then move across and link up with the West Beach force. Two more waves of helicopters would be required to deploy all of BLT 2/9 to Koh Tang. The flight from U-Tapao to Koh Tang was a four-hour round trip. It was estimated that only 20–30 Khmer Rouge were on Koh Tang; the information regarding the heavy anti-aircraft fire coming from Koh Tang and the number of gunboats present was not passed on to the Marines.[7]^:120–121 Preparatory airstrikes of the landing zones were ruled out for fear of hitting crewmembers who might be held nearby.[8]^:104 A unit of 57 Marines from D Company, 1/4 Marines together with volunteers from Military Sealift Command to get Mayaguez under way, an explosive ordnance disposal team and a Cambodian linguist would be transferred by three HH-53 Jolly Greens to the Holt which was scheduled to arrive on station at dawn for a ship-to-ship boarding of Mayaguez one hour after the assault on Koh Tang began.[7]^:122 Two additional CH-53s (because of their superior firepower, all the HH-53s were used for troop lift) were tasked as Combat Search and Rescue helicopters, supported by an EC-130 "King" airborne, command, control and communications (ABCCC) aircraft of the 56th Rescue Squadron.[7]^:119

USS Wilson was assigned to support the Koh Tang operation, and, after retaking Mayaguez, USS Holt would be deployed in a blocking position between Koh Tang and the Cambodian mainland with the mission of intercepting and engaging any Khmer reaction forces. U.S. Navy aircraft from Coral Sea were given the mission of striking targets on the Cambodian mainland to prevent interference with the rescue.[3]^:27

At 15:52 EDT (02:52 15 May Cambodia), President Ford convened the fourth and final NSC meeting regarding Mayaguez. General Jones briefed the NSC on the assault plan and plans for strikes by Guam-based B-52s on the port facilities at Kampong Som and the Ream Naval Base. Concerned that the use of B-52s might be excessive, President Ford limited the bombing to attacks by carrier-based aircraft commencing at 07:45 (Cambodia) and gave the go-ahead to the rescue plan.[7]^:123–124

USS Harold E. Holt pulls alongside SS Mayaguez to allow the boarding party to board

1/4 Marines board the Mayaguez

1/4 Marines reboard USS Harold E. Holt from SS Mayaguez

USS Harold E. Holt tows SS Mayaguez away from Koh Tang

At 06:13 on 15 May, the first phase of the operation began with the transfer by three HH-53s of D/1/4 Marines to the Holt. As the Holt slowly came alongside, USAF A-7D aircraft saturated Mayaguez with tear gas munitions. Equipped with gas masks, the Marines at 07:25 hours then conducted one of the few hostile ship-to-ship boardings by the U.S. Navy since the American Civil War, securing the vessel after an hour-long search, finding her empty.[7]^:185–188

U.S. Marines abandon their damaged helicopter Knife 22 in Thailand

East Beach with Knife 23 at left, Knife 31 at center and a destroyed Khmer Rouge Swift Boat at right

Knife 22 after emergency landing in Trat Province, Thailand

BLT 2/9 Command group disembarks Jolly Green 43 on the West Beach

Gig of USS Henry B. Wilson rescues USAF personnel

At 06:12, the eight helicopters (five CH-53 Knives and three HH-53 Jolly Greens) of the Koh Tang assault force approached the two Landing zones (LZs) on Koh Tang. At the West Beach, the first section of two CH-53 helicopters came in at 06:20. The first helicopter; Knife 21, landed safely, but while offloading its Marines came under heavy automatic weapons fire, destroying an engine. It managed to take off, protected by suppressive fire from the second CH-53, Knife 22, and ditched 1.6 km offshore. Knife 22 was damaged so severely that it turned back with its Marines (including the G Company commander) still aboard escorted by Jolly Green 11 and Jolly Green 12, and crash-landed in Trat Province on the Thai coast, where its passengers were picked up by Jolly Green 12 and returned to U-Tapao.[7]^{:159–162, 209–210}[9]^:248

At 06:30, the CH-53s approaching the East Beach encountered intense automatic weapons and RPG fire from entrenched Khmer Rouge. Knife 31 was hit by two RPGs, which ignited its left fuel tank and ripped away the nose of the helicopter. It crashed in a fireball fifty meters offshore. The copilot, five Marines, and two Navy corpsmen were killed in the crash, another Marine drowned swimming from the wreck and three Marines were killed by gunfire trying to reach the beach. A tenth Marine died of his wounds while clinging to the burning wreckage. The surviving ten Marines and three Air Force crewmen were forced to swim for two hours before being picked up by the gig of the arriving Henry B. Wilson.[7]^:195–197 Among the Marine survivors was the battalion's Forward Air Controller, who used an Air Force survival radio while swimming to direct A-7 air strikes against the island until the battery failed. The second CH-53, Knife 23, was hit by an RPG which blew off the tail section and crash-landed on the East Beach, but it successfully offloaded its 20 Marines and crew of five. They set up a defensive perimeter and the Knife 23 co-pilot used his survival radio to call in airstrikes, but they would remain cut off from both reinforcements and rescue for twelve hours.[7]^:162–167[9]^:248–249

Knife 32 was inbound to the East Beach when it was hit by an RPG and aborted its landing, instead heading out over the West Beach to the Knife 21 crash site where it dumped fuel and proceeded to rescue the three Knife 21 crewmen.[7]^:170–171 Two other sections of the first wave, consisting of the remaining four helicopters, were diverted from the East Beach to the West Beach and eventually landed all of their Marines between 06:30 and 07:00, although the final insertion by Jolly Green 41 required support from an AC-130 gunship in order to penetrate the Khmer Rouge fire on its fifth attempt. Knife 32, Jolly Green 41 and Jolly Green 42 eventually landed 81 Marines on the West Beach under the command of the company Executive Officer, and Jolly Green 43 landed 29 Marines of the battalion command post and mortar platoon a kilometer to the southwest.[9]^:250 By 07:00 109 Marines and five Air Force crewmen were on Koh Tang, but in three isolated beach areas and in close contact with Khmer Rouge troops. The Marines at the northern end of West Beach attempted to move down the beach to link up with Austin's command element to the south, but were beaten back by heavy Khmer Rouge fire which killed Lance corporal Ashton Loney.[7]^:176–178 While isolated, the Marines were able to use their 81 mm mortars for fire support and devised a makeshift communications network for controlling supporting air strikes by USAF A-7 and F-4 aircraft. It was decided that the platoon isolated on the East Beach should be extracted; following suppressive fire from an AC-130, Jolly Green 13 landed there at 08:15 amid a hail of machine gun fire. It had landed some 100 m away from the Marines who were reluctant to risk running to the helicopter, the helicopter took off again with its fuel lines ruptured and made an emergency landing in Rayong, Thailand.[7]^:175–176[9]^:249–251

Of the eight helicopters assaulting Koh Tang, three had been destroyed (Knife 21, Knife 23 and Knife 31) and four others damaged too severely to continue operations (Knife 22, Knife 32, Jolly Green 41 and Jolly Green 42). Of the helicopters used in the recapture of Mayaguez, Jolly Green 13 had been severely damaged in the East Beach rescue attempt.[9]^:249–251 This left only three helicopters (all HH-53s – Jolly Greens 11, 12 and 43) of the original eleven available to bring in the follow-up forces of BLT 2/9, so the 2 CH-53s (Knife 51 and 52) whose mission had been search and rescue – the last available helicopters – were reassigned to carry troops.[9]^:251 The five helicopters picked up 127 Marines of the second wave at U-Tapao between 09:00 and 10:00.[7]^:211–212 At 11:50 Knife 52, Knife 51 and Jolly Green 43 arrived over Koh Tang and prepared to land on the East Beach, as Knife 52 approached fire punctured its fuel tanks and the pilot aborted the landing and headed back to U-Tapao leaking fuel. Knife 51 and Jolly Green 43 also abandoned their landings and assumed a holding pattern.[7]^:213–214

At 06:07 the Khmer Rouge information and propaganda minister, Hu Nim, made a radio broadcast announcing that Mayaguez and her crew would be released. The section of his communique on the release was:

Regarding the Mayaguez ship. We have no intention of detaining it permanently and we have no desire to stage provocations. We only wanted to know the reason for its coming and to warn it against violating our waters again. This is why our coast guard seized this ship. Their goal was to examine it, question it and make a report to higher authorities who would then report to the Royal Government so that the Royal Government could itself decide to order it to withdraw from Cambodia's territorial waters and warn it against conducting further espionage and protractive activities. This applies to this Mayaguez ship and to any other vessels like the ship flying Panama flags that we released on May 7, 1975.[5]^:162–166

The transmission was intercepted by the CIA station in Bangkok, translated and delivered to the White House by 07:15 (20:15 EDT).[7]^:189–190 The White House was skeptical of the Khmer Rouge message and released a press statement at 08:15 (21:15 EDT) saying that U.S. military operations would continue until the crew of Mayaguez was released. Secretary Kissinger had ordered a delay to an airstrike by planes from Coral Sea on the Kompong Som oil storage complex and Ream airfield.[7]^:190–193 At 06:30 on Koh Rong Sanloem the crew of Mayaguez were informed that they would be allowed to return to their ship, after having first agreed to a statement that they had not been mistreated.[7]^:179–183 At 07:15 Mayaguez's crew was loaded aboard the Thai fishing boat, Sinvari (which had been captured by the Khmer Rouge five months earlier) escorted by a second boat with Sa Mean and other Khmer Rouge. Once away from Koh Rong Sanloem the second boat picked up the Khmer Rouge guards from Sinvari and instructed the crew to return to Mayaguez and call off the American planes.[7]^:197–199 At 09:35 an orbiting P-3 Orion spotted Sinvari and Wilson was ordered to intercept it, originally thinking it was a Khmer Rouge gunboat. The P-3 then identified that Caucasians were aboard and at 09:49 Mayaguez's crew was brought aboard Wilson. Confirmation of the release of the crew was sent to the White House and at 11:27 (00:27 EDT) President Ford went on U.S. national television announcing the recovery of Mayaguez and the rescue of its crew, but obscuring the fact that the crew had in fact been released by the Khmer Rouge.[7]^:199–201[7]^:204–207

President Ford, at Secretary Kissinger's urging, declined to cancel the scheduled airstrikes on the Cambodian mainland until the Marines on Koh Tang had been withdrawn.[7]^:206 At 09:05 A-6A Intruder and A-7E aircraft from VA-22, VA-94 and VA-95 escorted by F-4N fighters of VF-51 and VF-111 aboard Coral Sea began the airstrikes, bombing landing barges and oil storage facilities at Kompong Som and cargo planes and T-28 Trojan aircraft at Ream airfield and boats at Ream naval base.[7]^:193

USAF pararescueman Wayne Fisk guides U.S. Marines to an HH-53

View of the West Beach from an HH-53

Marines of 3rd Platoon, Company G board Jolly Green 11 to evacuate the East Beach

The U.S. Joint Chiefs of Staff decided that, with the ship recaptured and the crew released, further reinforcement of Koh Tang was unnecessary and at 11:55 they ordered the U.S. forces to "immediately cease all offensive operations against the Khmer Republic [and to] disengage and withdraw all forces from operating areas as soon as possible". Hearing this order, the orbiting EC-130 ABCCC recalled the second assault wave. The helicopters with the second wave reversed course until Austin, on the ground on Koh Tang, convinced Burns that the reinforcements were necessary to prevent his units from being overrun; the order was rescinded at 12:10.[7]^:214–215

The second wave carrying the Marines from Knife 22 and a platoon from Company E had originally taken off at staggered times between 09:00 and 10:00, but with the reversal of course its arrival on Koh Tang was seriously delayed.[9]^:252 At 12:10 Knife 51, followed by Jolly Greens 43, 11 and 12 successfully landed 100 additional Marines and evacuated nine wounded on the West Beach, making a total of 225 Marines – 205 on the West Beach and 20 Marines and five airmen on the East Beach.[9]^:257 Around the same time Austin's isolated command unit planned a linkup of its small contingent with the bulk of Golf Company at the northern end of the West Beach. Using mortar fire and A-7 airstrikes to clear Khmer Rouge in the jungle between the two forces, it reached the G Company perimeter at 12:45.[7]^:215–217

By 14:00 firing on the West Beach had reduced substantially as Em Son had moved most of his men back from the beaches with only three man patrols maintaining pressure on the two Marine enclaves. Austin asked the ABCCC if he should attempt to push across the island (a distance of approximately 1,100 feet (340 m)[8]^:104) to link up with the isolated unit on the East Beach, but was advised that another helicopter pickup would be attempted first.[7]^:218–224 At 14:15 Jolly Greens 11 and 43 approached East Beach, but were repulsed by heavy fire. Jolly Green 43 had a fuel line damaged, but made an emergency landing aboard Coral Sea at 14:36, where it was repaired and returned to service by 17:00.[9]^:258 During the attempted landing by Jolly Green 43, fire was seen coming from a semi-submerged Swift Boat that had been shot up by an AC-130 the previous day, A-7 aircraft were called in to destroy the boat with their 20 mm cannon.[7]^:225–226 At 16:20 hours, Nail 68, an Air Force OV-10 forward air control (FAC) aircraft, arrived and took over the direction of air support. At 16:23 Nail 68 called on Wilson to use its 5-inch gun to destroy the semi-submerged Swift Boat.[7]^:228 This change in controllers marked a turning point in the quality of airborne firepower available to the Marines, because for the first time that day they had an airborne observer exclusively dedicated to providing accurate and timely close air support.[9]^:257 At 17:00 Em Son gathered his forces and moved back up the island to secure an ammunition dump that lay between the West and East Beaches. He was surprised to find the dump intact and no Marines lying in ambush. Now resupplied, his men would be able to increase the pressure on the Marines again.[7]^:229–231

At 18:00 as the sun began setting a third attempt to rescue the East Beach force was attempted, using Jolly Green 11 as the rescue ship and with gunfire support from Jolly Green 12, Knife 51 and the gig from Wilson mounting four M60s. Nail 68 first ordered gun runs by an AC-130 followed by F-4s and A-7s along the edge of the East Beach, as this was going on five C-130s arrived over Koh Tang carrying BLU-82 "daisy cutter" bombs — a 15,000-pound device and the largest conventional explosive weapon in the U.S. arsenal at the time. Not seeing any practical use for the BLU-82s, Nail 68 ordered them dropped well south of the Marines' positions. At 18:15 Jolly Green 11 approached the East Beach, but did not actually set down because the hulk of Knife 23 was sitting on the beach; instead, the pilot (First Lieutenant Donald Backlund) skilfully hovered the helicopter several feet off the ground just north of the original beach LZ. The extraction was difficult because the helicopter would see-saw up and down. Only a few Marines at a time could board the helicopter's rear ramp in this fashion by timing their jumps to coincide with the downward motion of the aircraft. Jolly Green 11 was hit numerous times, but managed to transport its cargo of 20 Marines and five Airmen to the Coral Sea.[9]^:258 Shortly after Jolly Green 11 evacuated the East Beach, the first BLU-82 was dropped causing a huge explosion and sending a shockwave across the West Beach, Austin quickly called the ABCCC with the instruction that no more of the bombs should be dropped.[7]^:231–235 A report from Jolly Green 11 indicated that a Marine might be in the wreckage of Knife 31 and Jolly Green 12 went in to search for any survivors, Jolly Green 12 hovered above the wreck, while a crewman was lowered on a rescue hoist to survey the wreckage, no Marine was recovered and Jolly Green 12 suffered extensive damage in the rescue attempt and flew to Coral Sea.[7]^:235[9]^:259

As a moonless night fell over Koh Tang, the remaining two helicopters, Knife 51 and the hastily repaired Jolly Green 43, were joined by Jolly Green 44 that had been out of service at its Nakhon Phanom base but had been repaired and flown to the area. At 18:40 this force began to withdraw the remaining 205 Marines from the West Beach, protected by AC-130 fire and naval gunfire support from Henry B. Wilson and its gig. The first load of 41 Marines was lifted out at 18:40 by Knife 51 and flown to the Coral Sea, followed by 54 taken aboard Jolly Green 43. As Jolly Green 44 picked up a load of 44 Marines, the remaining Marines in the shrinking West Beach perimeter came under intense attack and were in danger of being overrun. The round trip to Coral Sea took thirty minutes, so the pilot, First Lieutenant Bob Blough, decided to deliver his Marines to Harold E. Holt, the nearest ship to Koh Tang, in complete darkness while hovering the helicopter over the ship with only its front wheels touching down. Within five minutes Jolly Green 44 returned and picked up 34 more Marines, leaving 32 still on the island; Jolly Green 44 was suffering engine trouble and this time headed for Coral Sea.[7]^:238–243

Finally, at 20:00 Knife 51 landed and began loading in the dark and under fire. Having loaded everyone save for themselves, Captain Davis and Gunnery Sergeant McNemar combed the beach looking for stragglers. Knife 51 Pararescueman Technical Sergeant Wayne Fisk was at the end of the ramp when two more Marines stumbled out of the darkness, Fisk asked Davis if all his men were aboard and he confirmed they were, but Fisk combed the beach one last time for stragglers. Finding none, he leaped onto the hovering CH-53 and at 20:10 Knife 51 left Koh Tang for the Coral Sea.[7]^:243–248[9]^:262

U.S. estimates of Khmer Rouge casualties were 13–25 killed on Koh Tang with an unknown number killed on Swift Boats and on the Cambodian mainland.[7]^:313–314

U.S. casualties were 10 Marines,[18][19][20][21][22][23][24][25][26][27] two Navy corpsmen,[28][29] and an Air Force crewman[30][31] killed in the crash of Knife 31; an Air Force crewman[32] killed in the crash of Knife 21; one Marine killed in action[33] on the West Beach; and three Marines missing in action and presumed dead.[5]^:81[34][35][36] Fifty were wounded[5]^:81 including thirty-five Marines and six airmen. In addition, eighteen USAF Security Police and five flight crew were killed in the CH-53 crash on the way to U-Tapao.[37]

Between 1991 and 1999, U.S. and Cambodian investigators conducted seven joint investigations, led by the JTF-FA. On three occasions Cambodian authorities unilaterally turned over remains believed to be those of American servicemen. In October and November 1995, U.S. and Cambodian specialists conducted an underwater recovery of the Knife 31 crash site where they located numerous remains, personal effects and aircraft debris associated with the loss. USS Brunswick, a U.S. Navy salvage vessel, enabled the specialists to conduct their excavation offshore. In addition to the support provided by the Cambodian government, the Government of Vietnam also interviewed two Vietnamese informants in Ho Chi Minh City who turned over remains that were later positively identified. As a result of these investigations the remains of Second Lieutenant Richard Vandegeer, Lance Corporals Gregory S Copenhaver and Andres Garcia and Privates First Class Lynn Blessing, Walter Boyd, Antonio R Sandoval and Kelton R. Turner were identified.[9]^:316–324[38] In 2012 the remains of PFC James Jacques, PFC Richard W Rivenburgh and PFC James Maxwell were identified.[39]

Four Airmen were awarded the Air Force Cross for their actions during the battle:

• Captain Rowland Purser, pilot of Jolly Green 43[40]
• First Lieutenant Donald Backlund, pilot of Jolly Green 11[41]
• First Lieutenant Richard C. Brims, pilot of Knife 51[42]
• Staff Sergeant Jon Harston, flight mechanic of Knife 31[43]

Second Lieutenant James V. McDaniel, platoon commander of Company G, 2/9 Marines was awarded the Navy Cross.[44]

Two Airmen and four Marines were awarded the Silver Star:

• Technical Sergeant Wayne Fisk, a pararescueman on Knife 51.[45]
• First Lieutenant Bob Blough, pilot of Jolly Green 44.[46]
• Lieutenant Colonel Randall W. Austin, the commanding officer of 2/9 Marines.[47]
• First Lieutenant Michael S. Eustis, USMC, the artillery liaison officer of 2/9 Marines.[48]
• First Lieutenant James D. Keith, USMC, the executive officer of Company G, 2/9 Marines.[49]
• First Lieutenant Terry L. Tonkin, USMC, the forward air controller of 2/9 Marines.[50]

Although the Mayaguez incident did not occur in Vietnam, it is commonly referred to as the last battle of the Vietnam War. However, U.S. military personnel who participated in it are not eligible for the Vietnam Service Medal by virtue of participating in that battle alone. The Armed Forces Expeditionary Medal is authorized instead for military members who participated in the battle. A congressional bill was introduced in 2016 to award veterans of the Mayaguez battle the medal, but the bill was referred to committee, effectively ending it.[51][52]

The U.S. air attacks destroyed a large part of the Khmer Navy and Air Force weakening them for the ongoing conflict with Vietnam over the disputed islands. In mid-June Vietnam attacked Poulo Wai and fought the Khmer Rouge before withdrawing in August and recognising it as Kampuchean territory.[1]^:198[2] Relations between the two countries improved thereafter until early 1977 when the Kampuchean Revolutionary Army began attacking Vietnamese border provinces, killing hundreds of Vietnamese civilians which eventually resulted in the Cambodian–Vietnamese War starting in December 1978.[1]^:304

For the Khmer Rouge leadership the fact that the U.S. attacked them even after they had announced the release of the Mayaguez and its crew, combined with memories of U.S. bombing of Cambodia prior to August 1973 reinforced their beliefs that the U.S. "imperialists" were determined to undermine their revolution.[1]^:198 The increasingly paranoid Khmer Rouge presumed that any foreigners captured in the country and purged Khmer Rouge (including Hu Nim), were CIA spies and would torture them at Tuol Sleng until they obtained confessions confirming their beliefs after which they would be executed.[1]^{:267, 276}

As news of the operation reached Bangkok protests began outside the U.S. Embassy.[53] U-Tapao air base had been used by U.S. rescue forces despite an explicit refusal of permission by the relatively new civilian Thai government of Sanya Dharmasakti.[5]^:55–60 After being refused by the Thai government, the US sought and obtained permission from the Thai military to proceed, resulting in considerable anger towards the United States. The Thai government called the act a violation of Thailand's sovereignty and called for the immediate withdrawal of all U.S. forces from U-Tapao.[7]^:256 As a result, the USAF implemented Palace Lightning and all USAF bases were closed and the last USAF personnel left Thailand in June 1976.

The reaction of the American public was favorable with President Ford's overall approval rating rising 11 percentage points.[54][55][56]

Some congressmen were dissatisfied with the level of consultation they received under the War Powers Resolution. Senator Mike Mansfield was the most critical, saying "we were informed, not consulted". In 1977 Senator Thomas Eagleton introduced an amendment to the War Powers Resolution that added the rescue of nationals to the list of situations not requiring prior approval by Congress, but also stipulating that only minimum force would be used in rescue.[5]^{:46,60–63,72–73,168–170} Eagleton's proposed amendment did not pass and similar amendments have been proposed since but also not progressed.[57]

On 23 June 1975, the House of Representatives Subcommittee on International Political and Military Affairs asked the General Accounting Office to review all aspects of the incident. On the War Powers Resolution, the General Accounting Office report's assessment was "The available evidence suggests less than full compliance with Section 3 [of the War Powers Resolution]."[58]

The U.S. military received much criticism for its handling of the incident.[59] In addition to the failure of intelligence to determine the whereabouts of the crew of Mayaguez and the presence of a sizable hostile force on Koh Tang, the timing of the operation was questioned until it became clear that combat had been underway four hours before the crew was released. Within the services, the Marines in particular were critical of the ad hoc nature of the joint operation and the perceived pressure from the Administration for hasty action,[60] although the success of Operation Frequent Wind had been the basis for many decisions made during the crisis. Vice Admiral George P. Steele, the Seventh Fleet commander, later stated that: "The sad part of the Mayaguez is that we had sufficient force coming up with the Seventh Fleet, after it had been turned around from the evacuation of Vietnam stand down, to seize Southern Cambodia. I begged for another day or two, rather than commit forces piecemeal as we did .... The idea that we could use U.S. Air Force air police and Air Force helicopters as an assault force appears to me as ridiculous today as it did then."[9]^:239

When many of the coordination and communications problems arose again during Operation Eagle Claw, the hostage rescue mission in Iran in 1980, significant changes in joint and special operations were brought about.[7]^:313

In April 1977 some Mayaguez crew members brought lawsuits in admiralty law at the San Francisco Superior Court against Sea-Land Service Inc relating to the incident. The crew members claimed that Captain Miller was derelict in his duty by "recklessly venturing into known dangerous and hostile waters of foreign sovereignty (Cambodia)" inviting the capture. Evidence was provided that Mayaguez was not flying a flag, and had sailed about two nautical miles off Poulo Wai. In June 1977, a settlement was reached. In February 1979 another settlement was reached by other crew members, making a total settlement of $388,000 to the crew members taking legal action.[6]

Former Knife 22, number 68-10928, upgraded to MH-53M Pave Low on display at Memorial Air Park, Hurlburt Field, Florida

In 1996 the Mayaguez-Marine Corps Memorial was dedicated in the grounds of the U.S. embassy in Phnom Penh by then Ambassador Kenneth M. Quinn and Senator John McCain. The memorial lists the names of the 18 U.S. servicemembers killed and missing at Koh Tang, along with Marine Security Guard Sergeant Charles "Wayne" Turberville, who was killed in a Khmer Rouge grenade attack on 26 September 1971.[61] The former Knife 22, number 68-10928, upgraded to MH-53M Pave Low is on display at Memorial Air Park, Hurlburt Field, Florida.[62]