The men of the SEAL platoon were all combat veterans, some with multiple tours of duty in Southeast Asia. They had already been conducting training operations in Korea during their deployment and the SEALs had already experienced time on the
Grayback
. In mid-February, the platoon was picked up by the submarine at Okinawa and cruised to the Philippines. There, they operated with the detachment from UDT Eleven as well as spent time in jungle and survival classes before conducting training with the Philippine Navy special operations units. In March, the platoon began heading back north. During their initial time on the
Grayback
, the SEALs and the crew of the sub enjoyed a short stay in Hong Kong as a break from their duties. It was soon enough that the SEALs returned to their training.
The mountain climbing Alfa platoon experienced in Korea was not going to be among the skills used when they received orders to report to Subic Bay. They would be a significant portion of Operation Thunderhead and were being involved with some of the earliest Navy preparations for the mission. Alfa platoon arrived at the huge U.S. naval base well before the SR-71s conducted their mission high across the skies of North Vietnam.
On April 10, Alfa platoon was once again picked up by the
Grayback
from Okinawa for a three-day cruise to the Philippines. Once the platoon arrived at Subic, the SEALs started training almost immediately after receiving briefings on their new mission assignment. In spite of each of the members of Alfa platoon holding a high security clearance, none of the men was told the real objective for the upcoming operation. Instead, the SEALs were eventually told that they would be conducting a demolition operation in retaliation for a North Vietnamese strike against U.S. naval assets in the Tonkin Gulf.
In mid-April, the USS
Buchanan
had taken fire from North Vietnamese 152mm gun batteries located in the Do Son Peninsula at Haiphong Harbor. The shelling had resulted in one seaman being killed and seven wounded. The SEAL operation would reportedly be conducted against the gun battery on the Do Son Peninsula. The general plan called for the SEALs to launch from the
Grayback
in Z-birds (inflatable rubber boats). A pair of swimmer-scouts would go onto the beach and conduct the initial reconnaissance. Depending on what the pair found in the immediate area, the rest of the force would be called in by infrared signaling devices concealed in the hands of the scouts. The men were told that there was a North Vietnamese Army garrison for the guns, and the whole platoon knew that an all-out firefight was something they should avoid if at all possible. On the peninsula, the SEALs would patrol to the gun batteries and destroy them, then withdraw and return to the
Grayback
in the rubber boats.
Though some of the SEALs wondered why the mission against the gun batteries was being conducted in a ground operation rather than by aircraft or naval gunfire, they trained for the operation thoroughly and professionally. The men who would be conducting the swimmer-scout insertions conditioned themselves by swimming miles every day. Two of these men were Frank Sayle and Tim Reeves. They swam for hours in the waters off Subic until they reached a level of fitness close to that of Olympic-class competitors.
Using their rubber boats, the SEALs conducted launch-and-recovery operations from the
Grayback
. Rendezvous with the submarine were conducted in complete darkness, utilizing specialized infrared signaling and detection equipment. The men paddled their rubber boats with the strength of their arms driving the small craft across the water. There were also outboard motors that could be used on the rubber boats. One of the motors, a specially silenced fifteen-horsepower motor, never seemed to work properly and was considered unreliable. Paddles always worked, and the men of the teams had learned their use very early on their initial training.
As a practical exercise, the SEALs conducted a number of full-dress nighttime insertions and patrols. Fully camouflaged and armed, the SEALs followed their swimmer-scouts onto land and went incountry, passing local villages whose occupants had no idea they were about. With a suppressed shot from a Mark 23 9mm Hush Puppy pistol on one patrol, a duck was killed before it could make a sound in alarm at the approaching green-faced men. Not even the quiet thud of the shot caused any alarm in the villagers as the SEALs continued their exercise. The men were silent in their movements, little more than dark shadows passing through the jungle. Their confidence in their own abilities was very high; they knew what they were capable of.
There was very limited training with the SDVs aboard the
Grayback
during Alfa platoon's time at Subic Bay. A detachment of men from Underwater Demolition Team Eleven was assigned to the
Grayback
and would be operating the SDVs. For most of the SEALs, their experience with an SDV consisted primarily of a walk-through, an examining of the boats while they were on their transportation trailers prior to being loaded on board the submarine. During the training at Subic Bay, there was no mention to the men of Alfa platoon about utilizing the SDVs in any upcoming operation. The SEALs knew that if they were involved with SDV operations, it would be as passengers rather than active crews of the small underwater craft. All they would have to do with the craft was get in and out, and that involved little more than opening the sliding hatch cover.
The UDT operators continued their training with the SDVs separately from the SEALs. Along with members of the
Grayback
's crew, the UDT operators practiced launching and recovering the SDVs. The bow hangars had a wet side and a dry side. The wet side could be pumped out and the SDVs worked on while sitting in their launch cradles. This way, the batteries could be recharged and the pressure in the breathing air tanks brought up to peak. There was also the necessary maintenance of the equipmentâan everyday fact of life in the Navy, and particularly in the SEAL and UDT teams. When you worked underwater, your life depended on your breathing equipment. If you didn't maintain that, death was a certainty. So the philosophy of constant maintenance was an easy one to connect with every facet of their operating in the teams, whether on dry land, in the air, or underwater.
Training could be long, dull, and repetitive during the more than six weeks that the SEALs prepared for their upcoming mission. But the men of the teams were professional in all of their actions; they conducted the training until they were perfect at it, and then worked to improve on that.
After Lieutenant Commander Towers had come and gone from the
Grayback
, all of the men were taken back on board and the submarine made sea-ready. The twelve enlisted men of the SEAL platoon were being led by two officers: Lieutenant Melvin S. Dry was the officer in charge of the platoon, and his assistant was Lieutenant Robert J. Conger Jr. The chief petty officer of the platoon was Philip L. “Moki” Martin. All of the leadership of the platoon had multiple combat tours behind them and knew what to expect of their men in any conceivable circumstance. In spite of the trust they had for each other, there was a limit imposed from higher command on just what all of the SEALs could be told, even when their mission briefing took place after the submarine had left port.
There was no place on board a submerged submarine where a secret could be leaked out to the enemy. But Operation Thunderhead was a unique situation in more ways than one. Only the officers and a couple of the enlisted men were told the entire mission profile. All of the rest of the team were told what they needed to know in order to conduct their part of the mission. And the mission sounded like it would be a hairy one, or at least there was the very real possibility of a raised pucker factor if things went south in a hurry.
The story of the demolition operation against the gun batteries was now abandoned, in spite of the men having loaded volumes of explosives and demolitions into the special magazines on board the submarine. Now the men were told that they were to go out and land on an island near the mouth of the Red River. Eventually they were told that they wouldn't be conducting the operation from the rubber boats they had trained with. For the utmost in secrecy, they would conduct the infiltration by launching an SDV from the
Grayback
while she was submerged. Moving underwater at night, the SEALs and the UDT operators would head for the island where the SEAL element would exit the SDV. With only light weapons with which to defend themselves, the SEALs would conduct an observation post, looking for the red flag or red light on any local small watercraft. Using their own judgment, the SEALs would make contact with the indicated small craft after reporting in to higher command. The object of their attention was going to be high-ranking Chinese or North Vietnamese defecting to the United States.
There was no mention of escaping POWs; originally only a few members of the platoon and UDT detachment, primarily the officers, were even informed that their original mission had changed from one of demolition to that of recovery. The rest of the platoon was brought up to speed on the new mission, or at least some of what the new mission would be. There were strong suspicions among members of Alfa platoon that they were not being told what was actually going on.
While the SEALs were on the island, the
Grayback
would remain submerged at a distance of only a few thousand yards from the island. The specific location of the submarine layup point would be dependent on the best judgment of Commander Chamberlain regarding the safety of his boat and crew.
Presented in those terms, it didn't seem like an excessively difficult mission. The real danger came in the fact that the entire operation would take place in the national waters of North Vietnam. On top of the threat of enemy detection, the SEAL element would be conducting their observation post on an island known to be occupied by North Vietnamese. But the existence of a North Vietnamese naval base, and even the small native fishing village on the island, was kept from the SEALs not directly conducting the initial parts of the operation
The basic mission was one that the SEALs were very experienced with; the observation and listening post mission had been conducted hundreds of times on deployment in South Vietnam. It would be nothing new for the men to work behind enemy lines, possibly surrounded by hostile forces. It was through missions like that and even more hazardous ones that the SEALs had developed a reputation of a unit to be feared by the Viet Cong and NVA. But this operation would be taking part so far behind the lines that they couldn't even be seen over the horizon.
It was the fear of possible capture and interrogation of the SEAL element on the island that had caused higher command to order the compartmentalization of mission information. If they were captured and made to talk, if the men didn't know that there was going to be a POW escape, they couldn't tell anyone about it. That would at least help minimize the North Vietnamese suspecting and looking for a possible intelligence net involving the prison camps. The cover story about high-ranking defectors was a plausible one and would also help deflect a North Vietnamese search for hard-won intelligence assets in their own country.
As the
Grayback
traveled underneath the U.S. Seventh Fleet, there was time for a small distraction from the pressure of the upcoming operation. In a message received shortly before their leaving port, Moki Martin had been informed that he would be promoted to the rank of warrant officer. The close-knit makeup of the SEALs made for a certain level of familiarization between the officers and the enlisted men. They were far more casual in their interactions than most of the rest of the Navy. An example of this was that Lieutenant Dry was known as Spence to his men, in spite of his being a commissioned officer and a class of 1968 graduate of the U.S. Naval Academy.
There are traditions in the Navy, and they were not going to be ignored on board the
Grayback
. Martin's orders had read that his promotion would be effective the first of June. On that day the wardroom of the
Grayback
was cleared out and a small celebration took place. With a cake baked for the event, Philip Moki Martin was welcomed by the officers of the
Grayback
, SEAL, and UDT platoons, to the ranks of the Officer Corps of the United States Navy.
The trip to the operating area off the coast of North Vietnam was an uneventful one for the SEALs. They had nothing to do in regard to the operation of the submarine and it was far too crowded to conduct the near religion of the SEALs: physical fitness exercises. Lieutenant Dry was the son of a Navy submarine skipper and he was more than relaxed among his men aboard the
Grayback
. To pass the time, the SEALs gathered up the movies they had brought on board from the base at Subic. The seventy-five films were watched over and over again in the SEALs' living quarters. Davis was the man whose bunk was closest to where the projector was set up, resulting in his becoming the platoon's projectionist. Some of the favored films of the platoon included
Vanishing Point
, which highlighted a long, high-speed car chase across the American West. To make the films more entertaining after having seen them repeatedly, they were run backward. Instead of a fiery crash ending a scene, a racing car was born from the consuming flames. Moki Martin had a particular liking for two of the movies,
Vanishing Point
and
Two-Lane Blacktop
. But even he started to think that all of the films were just kind of blurring together as the sub continued on toward North Vietnam.
Distractions were needed by the SEALs to help keep them from noticing some of the details involved in living effectively as passengers onboard the
Grayback
. The living quarters in the hangar spaces were constantly damp; there was no real way to dry them completely while the submarine was under way. The humidity resulted in a mildew smell that permeated the compartment. But the mildew was not the only noticeable smell; when the submarine surfaced her snorkel to run the diesel engines, the air was also used to vent out the boat. The only trouble with venting the boat was that the air circulation system resulted in the forward head venting through the SEALs' compartment. The announcement to “vent the boat” made many of the unconventional warriors practice their breath-holding abilities as they looked for sources of fresher air.