When President John F. Kennedy established the Navy SEALs in 1962, he envisioned a force capable of unconventional warfare, small, highly trained units that could operate in jungles, rivers, and coastal waters where traditional forces struggled. Vietnam became their proving ground.
The SEALs quickly earned a reputation as “the men with green faces,” a nickname given by the Viet Cong for their camouflage paint and stealth tactics. They conducted reconnaissance, ambushes, and direct-action missions in the Mekong Delta, often working in small teams of four to six men. Their operations were dangerous and intimate, close-quarter firefights in swamps, villages, and rivers where escape routes were few. By the late 1960s, SEALs had become one of the most feared and respected units in the war.
Operation Thunderhead
By 1972, U.S. combat operations were winding down, but the plight of American prisoners of war remained urgent. Many of these men were confined in the notorious Hỏa Lò Prison in Hanoi, grimly nicknamed the “Hanoi Hilton” by its captives.
Conditions inside were harsh. Prisoners endured isolation, beatings, and deprivation. But the will to escape never fully disappeared. Among them was Air Force Colonel John A. Dramesi, who had already attempted an escape in 1969. Intelligence suggested that Dramesi and others were planning another breakout from Hỏa Lò, intending to steal a boat and travel down the Red River to the Gulf of Tonkin.
To support this daring plan, the Navy launched Operation Thunderhead, a highly classified mission involving SEAL Team One and Underwater Demolition Team 11 (UDT-11). The submarine USS Grayback, modified to carry SEALs and their Swimmer Delivery Vehicles (SDVs), was chosen as the launch platform.
The USS Grayback had an unusual history. Originally commissioned in 1958 as SSG-574, a guided missile submarine designed to carry Regulus cruise missiles, she was later converted in 1969–1970 into a transport submarine for special operations. After this transformation, she was redesignated LPSS-574 (Landing Platform, Submarine). By the early 1970s, Grayback had become one of the Navy’s most secretive assets, outfitted to deploy SEALs, UDT teams, and SDVs directly from her hull. This conversion made her a critical tool for clandestine missions like Thunderhead, where stealth and the ability to insert small teams close to enemy shores were essential. Grayback’s role in the operation reflected the growing importance of submarines in special warfare, a precursor to the modern use of subs as covert platforms for SEAL delivery.
The Mission Unfolds
The plan was audacious. SEALs would deploy at night from the submerged submarine, using SDVs to reach the shore undetected. Once ashore, they would rendezvous with the escaping POWs and guide them to safety.
But from the start, the mission was plagued by difficulties. Intelligence was incomplete, the seas were rough, and the SDVs suffered mechanical problems. Communication with the POWs never materialized. The SEALs pressed on, knowing that capture meant torture or execution.
On June 5, 1972, tragedy struck. Lieutenant Melvin Spence Dry, leading the SEAL element, drowned when his SDV surfaced too far from the submarine in heavy seas. Despite desperate rescue efforts, Dry was lost. His death marked the final combat loss of a Navy SEAL in Vietnam, closing a chapter of sacrifice and valor.
Secrecy, Aftermath, and Legacy
Operation Thunderhead remained classified for decades, its details hidden even from families. Dry’s father, retired Navy Captain Melvin H. Dry, spent years seeking answers about his son’s death. Only in the early 2000s did the mission’s story emerge publicly. In recognition of his bravery and sacrifice, Lieutenant Melvin Spence Dry was posthumously awarded the Bronze Star Medal.
Though the mission failed to rescue POWs, it symbolized the SEALs’ ethos: no man left behind, no mission too dangerous. It was a final act of courage in a war that had tested the limits of America’s special operations forces.
The Vietnam War transformed the SEALs from experimental units into a permanent fixture of U.S. military power. Their experiences in the Mekong Delta, coastal raids, and missions like Thunderhead forged the tactics and traditions that define Naval Special Warfare today.
Final Thoughts
Operation Thunderhead was a daring, desperate mission that reflected both the ingenuity and the risks of special operations in Vietnam. Lieutenant Melvin Spence Dry’s sacrifice remains a poignant reminder of the cost borne by SEALs in their commitment to rescuing comrades. His death marked the end of SEAL combat losses in Vietnam, but the lessons of the war ensured that the SEALs would emerge stronger, shaping their legendary role in conflicts to come.