Operation Thunderhead (32 page)

The SDV was a small, black fiberglass craft that could carry a crew and Navy SEALs much farther and faster than the men could possibly swim. And the little submersibles could be launched from the hangars of the
Grayback
while she was still submerged. The wet side of the hangars was about twenty feet long and could hold two SDVs on their launching cradles. A transfer lock on the bow bulkhead of the wet-side chambers could hold two personnel and flood or drain to allow passage between the wet and the dry side of the hangar while undergoing operations. The dry side of the hangar was an area about twenty-five feet long where equipment was stored. There were bunks for the special operations personnel, deployed SEALs using the port-side hangar, and the UDT detachment using the starboard-side hangar. The starboard-side hangar was fitted with a ten-foot-long decompression chamber for use during underwater operations. The port hangar held additional storage areas in the same space. Both hangars were connected to the interior of the
Grayback
through waterproof hatches.

Stationed at Subic Bay in the Philippines, the
Grayback
was constantly in use practicing and training with the SEALs and a UDT detachment assigned to her. There were additional operations conducted with both Army Special Forces and Marine Force Recon units off the unique boat. And she was only a relatively short cruise to the waters of the Gulf of Tonkin and the shores of North Vietnam.

The suggestion for the use of the submarine had come from Earle, who also knew the skipper of the boat, Commander John Chamberlain. At that moment, the
Grayback
was in port at Subic Bay. It was a relatively easy matter to just call down to the boat. The problem came with just what could be said in the conversation. Within a matter of only a minute, the only thing Chamberlain could say over the open line was that there was a question of whether the
Grayback
would be available for the specified time period.

The remaining details that had to be discussed with the skipper of the
Grayback
would have to wait until there could be a face-to-face meeting between him and Towers. At the local Submarine Ops office, Towers was able to learn a little bit about the
Grayback
, but the specific capabilities about the submarine, the SDVs, and the men who would operate them had to wait until the scheduled meeting at Subic Bay on May 22.

The planned escape time for the prisoners was for sometime between June 1 and 15. Whatever watercraft the escapees would be able to secure, they knew to signal with either a red or a yellow flag during the day. At night, the signal would be an arrangement of red lights.

To ensure that there would be assets on site to assist the escaping prisoners, there would be at least several days' overlap for the mission on either end of that window. The basic mission profile that was put together by Towers centered about the conduct of surveillance operations running from May 29 to June 19.

The surveillance area for the operation was very large, covering nearly fifty miles long and including both the mouth of the Red River as well as all of the estuaries of the secondary rivers and waterways that connected to it downstream of Hanoi. The size of the area was large in part due to the suspected lack of navigation capability on the part of the escaping prisoners.

Back at the Hanoi Hilton, Dramesi planned to follow the Red River to the ocean waters, but to account for the various tributaries and forks in the flow of the river, the escapees would consistently take the right-side choice to continue on their way.

The primary units conducting the surveillance would be HH-3A search-and-rescue helicopters and the SEAL units deploying from the
Grayback
. The helicopters would operate off of their parent carriers, but almost no one on the surface ships of the fleet would know about the SEALs' involvement; nor would they be told that there was an American submarine operating in the area.

Only a small handful of officers were briefed on what was really the objective of the operation. A cover story was used to brief all of the other personnel who had to have some knowledge of the mission in order to conduct their parts of the operation: The mission was to recover defectors from North Vietnam, people who had held high government offices. Even if by some means the North Vietnamese heard about such a mission, they would be spending their time trying to locate who the defectors were rather than increasing the security of the prison camps.

The primary ships used in Operation Thunderhead were relatively few in number. The USS
Long Beach
(CGN-9) was a nuclear-powered guided missile cruiser with a complement of nearly 1,000 officers and men. She would be the command ship for the operation, and her captain would be one of the men given a full briefing on the actual target of the operation. The USS
Harold E. Holt
, a Knox-class fleet escort ship, would be part of the supporting units for Thunderhead. The
Holt
had a hospital unit on board so it would receive the POWs once they were recovered and transport them to Subic Bay. The ship carried a primary armament of one forward Mark 42 mount with a single five-inch gun. The cannon could put out a more than seventy-pound high-explosive shell to a range of over fourteen miles.

Detachment 110 of Helicopter Support Squadron Seven (HC-7) was assigned to operate off the aircraft carrier USS
Midway
as a combat search-and-rescue (SAR) unit. The HH-3A Sikorsky Sea King helicopters of the HC-7 detachment were armored and armed with a 7.62mm minigun as well as M60D machine guns. The minigun is a rotating-barrel, high-rate-of-fire machine gun that can spit out rounds at a gunner-selectable cyclic rate of 2,000 or 4,000 rounds per minute. On board the HH-3A helicopter, the minigun fed from a 2,000-round box of belted 7.62mm ammunition and was mounted at the starboard-side hatch. The two other machine guns on board, the M60Ds, fired the same ammunition at a much more sedate cyclic rate of 550 rounds per minute and were mounted at the port side and stern. The SAR helicopters were the primary surveillance platforms for the operation and would perform the rescue/extraction of the escaped POWs once they were located.

The only naval assets that were assigned solely to Operation Thunderhead were the submarine
Grayback
and the UDT and SEAL detachments aboard her, and Lieutenant Commander Towers, the officer in charge (OIC) of the operation. All the other naval craft and crews would be conducting their regular missions, taking the war to the North Vietnamese. During the time period that Thunderhead would be active, there would be air strikes conducted against targets in North Vietnam. These ALFA strikes would also be conducted on and around Hanoi itself. It was hoped by Towers and the other officers involved with Thunderhead that the ALFA bombing around Hanoi would help give cover to the POWs for their escape attempt.

The search and surveillance for the POWs would be conducted by SAR helicopters in addition to their regular duties. There would be two to four flights a day through the target area, varying in the time they spent in the air and when they passed through the area. No matter when or how long the helicopters flew, they would cover 100 percent of the search area, which extended from west of the “Hourglass” River to north of the Red River—a coastal area that ran from 19 degrees 58 minutes North/106 degrees 02 minutes East at its southern end near the Hourglass River to 20 degrees 30 minutes North/106 degrees 35 minutes East at the far northern end past the Red River.

The flights would be on watch for any small craft waving a red or a yellow flag. The SAR helicopters would operate under the call sign “Big Mother” while conducting their surveillance mission. Any identified small craft would be immediately reported to the OIC (Towers), identified by the call sign “Hernandez.” Once the flag was reported, the helicopter crew was authorized to do whatever was necessary to further identify the occupants of the craft. If fired upon, they could return fire and call in fire support as necessary.

The SEALs would have a much more difficult and dangerous mission to perform: A two-man SEAL element would be landed on an island known to be held and occupied by the North Vietnamese. The island was located at 19 degrees 54 minutes North/106 degrees 05 minutes East and was in a central location to observe the primary site where the POWs were expected to appear. Once in place on the island, the SEALs would man a twenty-four to forty-eight-hour observation post. The SEAL element would be rotated by slipping in a new team by SDV and removing the previous team back to the
Grayback
. All of these actions by the SEALs, the SDVs, and the
Grayback
would be conducted within North Vietnamese waters. The details of just how the island observation portion of the mission would be conducted were left in the hands of the SEAL officers and the commander of the
Grayback
. The
Grayback
had the call sign “Panther,” and the SEAL element would be identified as “Tom Boy.”

Daily situation reports on the conduct of the operation would be sent by Towers to the Chairman of the Joint Chiefs of Staff, the Commander in Chief of the Pacific Fleet, and the Commander of the Seventh Fleet, Admiral Moorer, Admiral Gaylor, and Vice Admiral Holloway, respectively. The messages would be sent Top Secret SPECAT (Special Attention).

After meeting with Commander Chamberlain and briefing him on the details of Operation Thunderhead, Towers had the capabilities of the
Grayback
, her SDVs, and the personnel of Naval Special Warfare explained to him.

The SDVs were the Mark VII Mod 6 models, known to the men who used them as “Six Boats.” Each of the black-hulled craft were wet-type submersibles. That meant they flooded with water and each person aboard had to wear breathing apparatus while operating. The Six Boats carried a crew of two, a driver and a navigator, and two fully equipped SEALs. The fiberglass Six Boats were more than eighteen feet long, almost three feet wide, and less than five feet tall. Operating and riding in one meant a long, cold trip underwater breathing air from the eight ninety-cubic-foot tanks on board. The air was enough to supply the four men on board with breathing gas for three hours at a normal usage level. That time underwater could be extended by the men breathing from their own personal breathing systems normally used for entering or exiting the craft. The six silver-zinc batteries on the SDVs could move them through the water at a maximum of four knots for up to eight hours.

Each SDV weighed over a ton before including the crew, passengers, or their equipment. The craft were normally operated by crews from the UDT detachment on board the
Grayback
; the SEALs were the passengers. The central buoyancy tank of the SDV could be pumped out or water added to adjust the craft in the water. Sliding hatches covered the front and rear compartments of the SDVs, leaving the men within in a dim, wet environment. Lighting was held at a minimum to cut down on battery drain, and the cramped quarters meant that all of the men on board couldn't move about to keep warm. It was a claustrophobic, dark, difficult way to swim through the water unseen. But the SEALs and the UDT operators were trained to work with the Six Boats, and the
Grayback
had two of them available for Thunderhead.

The Grayback herself was more than unusual and had other aspects besides her bow hangars that made her particularly fit for the operation. As a diesel-electric boat, the Grayback could move silently through the water when required. Operating from batteries, the electric motors and other systems of the
Grayback
made her quieter than even the best nuclear submarines of the day. Her crew was expert in getting the very best performance from the sub they were all very proud of. There was an additional specification of the
Grayback
that would allow her to conduct the twenty-two-day-long planned observation mission.

The seawater intakes and outlets for the
Grayback
's machinery were not along the bottom of her hull, as they would be on most other submarines. The openings were up along the side of the
Grayback
's hull, where they could be run while the sub was sitting hull-down on the bottom. This meant that the critical machinery of the boat could remain running while the
Grayback
was sitting on, or more usually floating just above, the sea floor. Only when she needed to recharge her batteries would any part of the
Grayback
have to rise above the surface. At those times, she would rise up to just below the surface and extend an air-breathing snorkel. With her snorkel raised, the
Grayback
would quietly run her diesel engines, recharging the batteries until she submerged once again.

Like a huge steel alligator, the Grayback could wait silent and unseen underwater, only coming up to breathe at long intervals. Unlike a reptile, the Grayback could launch her SDVs while remaining submerged, the small craft coming out of the bow hangars as the great clamshell doors opened slowly. While inside the bow hangars, the black-hulled Six Boats could be serviced and prepared by men traveling in and out of the submarine through the bow hatches connecting the hangars to the interior of the boat. Once mission-ready, the SDVs would be winched out on wheeled dollies by men wearing underwater breathing gear and launched from the deck.

LAUNCH

Alfa Platoon of SEAL Team One was on deployment as the Naval Special Warfare Western Pacific Detachment (WESTPAC) on Okinawa when Operation Thunderhead was being laid out. The platoon of twelve enlisted men and two officers of Alfa platoon were the first contingency element sent out by SEAL Team One, there to conduct special operations in support of the U.S. Navy as the need arose. The deployment was supposed to be a normal one for the men of SEAL Team One, particularly now that the Vietnam War was winding down and the Navy was beginning to change its operational tempo from wartime to a peacetime footing. Alfa platoon was tasked with setting up the SEAL quick-reaction base facilities at White Beach on Okinawa as well as conducting training with special operations units of American allies in the area. The U.S. Navy base on White Beach was a large one, but there were no support facilities available to meet the SEALs' particular needs. Among the structures prepared by Alfa platoon was a diving locker and paraloft for the maintenance and preparation of parachutes. Several members of the platoon proved that their carpentry skills equaled that of their weapons-handling abilities.