Encountering stronger-than-expected defences on Koh Tang, three United States Air Force helicopters were destroyed during the initial assault and the Marines fought a desperate day-long battle with the Khmer Rouge before being evacuated.

[3]: 11 [5]: 104 The crisis began on the afternoon of 12 May 1975, as the U.S. container ship SS Mayaguez, owned by Sea-Land Service Inc., passed nearby Poulo Wai en route from Hong Kong to Sattahip, Thailand.

[7]: 27  Seven Khmer Rouge soldiers boarded Mayaguez and their leader, Battalion Commander Sa Mean, pointed at a map indicating that the ship should proceed to the east of Poulo Wai.

[7]: 36–39 They also wished to avoid comparisons to the Pueblo incident of 1968, where the failure to promptly use military force to halt the capture of a U.S. intelligence ship by North Korea led to an eleven-month hostage situation.

[7]: 39 Following the NSC meeting, the White House issued a press release stating that Ford considered the seizure an act of piracy, though this claim did not have a foundation in maritime law.

[5]: 41–170  Secretary of Defense James R. Schlesinger ordered the military to locate Mayaguez and prevent her movement to the Cambodian mainland, employing munitions (including tear gas and sea mines) if necessary.

Kissinger then instructed George H. W. Bush, the head of the U.S. Liaison Office in Beijing, to deliver the note to the Chinese Foreign Ministry and to pass on an oral message that "The Government of the United States demands the immediate release of the vessel and of the full crew.

[7]: 45 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.

[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]: 62 The 2nd Battalion, 9th Marines (BLT 2/9) (commanded by Lieutenant Colonel Randall W. Austin) was then on 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.

The Pakistani first secretary had told an American diplomat that a senior Chinese embassy official in Tehran said China was "embarrassed" by the Cambodian seizure of the Mayaguez and expected it to be released soon.

[8]: 76 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]: 95–96  The circling 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.

[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.

Alternatively, with the arrival of the USS Hancock in the area, a "coordinated assault at first light on 16 May would "carry lower military risks" and "enhance the prospects of quick success and minimize the loss of life."

[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.

[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.

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.

[3]: 27 In the afternoon in New York City, the US ambassador to the UN, John A. Scali, delivered a request for assistance to UN Secretary-General Kurt Waldheim that noted the US reserved the right to act in self-defense in accordance with Article 51 of the UN Charter.

[7]: 132–133 On their arrival at Koh Rong Sanloem Miller was taken to the senior Khmer Rouge commander where he was subject to a cursory interrogation before being asked if he could talk to the American planes from Mayaguez.

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.

[10]: 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.

With illumination rounds from Cambodian mortars, Fisk returned to Knife 51 where McNemar jumped aboard, and Knife 51, some 10 minutes after landing, departed Koh Tang for the Coral Sea[7]: 245–248 [10]: 262 [3]: 70 [14]: 141–144 Due to the intense direct and indirect fire during the operation, the bodies of Marines and airmen who were killed in action were left where they fell including LCpl Ashton Loney, whose body was left behind in the darkness during the evacuation of the West Beach.

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.

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.

[44] A US Department of Defense Factsheet of US MIAs in Cambodia dated April 27, 2021 reports: “Witnesses have assisted in identifying recovery sites on Koh Tang, the island associated with the Mayaguez incident.

[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 Operation Freedom Deal (U.S. bombing of Cambodia) prior to August 1973, reinforced their beliefs that the U.S. "imperialists" were determined to undermine their revolution.

"[65] The paramount objective during the crisis, as Scowcroft later explained, "was to make it clear, to everyone, to our friends, to potential opponents, that notwithstanding the fact that we had just withdrawn from Southeast Asia under fairly ignominious circumstances, if you will, that the United States understood its interests and was prepared to protect them."

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.