Lack of Training Aided USS Thresher’s Undoing

By D. Allan Kerr

Before Lieutenant Commander John Wesley Harvey took the helm of the submarine USS Thresher in January 1963, he was the executive officer aboard the USS Sea Dragon during an historic Arctic cruise.

Prior to that, he spent three years aboard the legendary USS Nautilus, the world’s first nuclear-powered naval vessel, during the 1950s. He was the sub’s reactor control officer in 1958, when the Nautilus became the first watercraft in history to reach the North Pole.

Before Lieutenant Commander Pat Garner stepped in as executive officer, or second-in-command, of the Thresher in December 1962, he took part in three epic cruises beneath the Arctic ice during more than four years aboard the nuclear submarine USS Skate. He was aboard the Skate in 1959, when she became the first sub to break thru the ice to surface at the North Pole.

Master Chief Petty Officer Benjamin Shafer served on a destroyer in the Pacific during the Second World War, but after volunteering for the submarine service he was a crewman aboard the submarines Cobbler and Skipjack. By April 1963, he had been aboard the Thresher for more than two years as an electrician’s mate. His brother John, a senior chief petty officer, joined the crew in September 1961.  

Chief Petty Officer Roscoe Pennington survived six submarine war patrols during the Second World War and was also a veteran of the Korean War. He was asked to serve as an instructor at the nuclear training program in New London, Connecticut, but reportedly turned this down to join the Thresher’s commissioning crew in 1961. Pennington was the sub’s chief nuclear reactor technician.

These are just a few of the 129 men, including civilian workers, who perished aboard the Thresher in April 1963 during the world’s worst nuclear submarine disaster.

“They were experienced, well trained, very smart and dedicated,” retired Navy Capt. Jim Bryant said recently, “but they lacked recent operational training, especially on the many configuration changes.”

There has long been speculation about what exactly went wrong during the fatal final dive of the Thresher 58 years ago this upcoming April 10th, about 220 miles off Cape Cod. Following a lawsuit led by Bryant, a former submarine commander, the Navy is now releasing documents which have remained classified for decades.

To date, no single “smoking gun” has been uncovered as to the accident’s cause by Bryant and other experts combing thru the released records. Instead. they believe a number of factors converged at the worst possible moment.

One of these contributing issues, they contend, is crew members’ lack of familiarity with the revamped Thresher following several months of repair, which prevented them from responding correctly when things started to go wrong. Because of the Cold War climate of the times, it now appears these sailors were not provided ample opportunity to get reacquainted with the sub’s systems.  

In writing about this famous sub over the past several years, I’ve often made a point of touting those lost aboard the doomed vessel as men of genius and adventure, the Navy’s best and brightest. They were, after all, charged with operating the most advanced weapon on the sea at that time, built at a cost of $45 million (in 1960s dollars). Admiral Hyman Rickover, the fabled “Father of the Nuclear Navy,” had personally selected several of the Thresher’s crewmen.

Bryant and retired naval architect Stephen T. Walsh, among others, recently took part in a webinar panel hosted by the Naval Historical Foundation to discuss their findings. I have to admit, I got a bit defensive when they cited inexperience as one of the possible causes of this terrible tragedy.

“You are confusing experience with training,” Walsh replied.

And one of the reasons this necessary training was cut short, they say, was a rush to get the Thresher back in the water at the very height of the Cold War with the Soviet Union.


By now, hopefully, most folks in the Seacoast are familiar with the basic facts of the Thresher disaster. With its iconic SSN 593 hull number, the Thresher was the very first submarine of its class, specifically built to hunt and destroy Soviet subs. 

SSN 593 was commissioned at the shipyard in August 1961 and promptly took her place in the fleet. She returned to Kittery in the summer of 1962 for what would turn out to be a nine-month major overhaul.

Designed and constructed right here at Portsmouth Naval Shipyard, this nuclear-powered fast-attack submarine was able to dive deeper and more quietly than any sub before her. She was armed with the most advanced weapons system of her time. Author John Bentley once described the Thresher as “a decade ahead of any other killer sub in the world.”

Her final cruise was intended to be a routine sea trial, including deep-dive tests to check out the sub’s systems. The sailors and civilian observers, including 13 employees of the local shipyard as well as three Navy officers from the facility’s military staff, all expected to be home for Easter Sunday that weekend.

Instead, the Thresher lost power and sank below its test depth, ultimately imploding under the immense pressure of the sea. The crew’s final moment occurred within one-tenth of a second, naval experts have said. The submarine now lies in shattered pieces across the ocean floor, beneath 8,400 feet of water.

As the first nuclear submarine ever lost at sea, occurring in the early days of the Atomic Age and the midst of the Cold War, the loss of the Thresher was front-page news all over the world. President John F Kennedy, who would himself be murdered just seven months later, ordered flags to be flown at half-staff. Recording artists like the Kingston Trio, Pete Seeger, Phil Ochs and Abner Jay all recorded popular ballads paying tribute to the submarine and her crew.

Almost immediately, the Navy launched a board of inquiry to determine the cause of the disaster, thru hearings conducted at the Kittery shipyard. Two months and 120 witnesses later, the Navy announced the Thresher’s loss was “most likely” due to a piping failure in one of the sub’s salt water systems, possibly the engine room. The resulting spray and flooding shut down her electrical circuits and the Thresher lost power, sinking to her fate, the Navy determined.

But as there were no survivors and the incident took place more than 1,000 feet below the surface, other theories have been offered in the decades following the tragedy. One indisputable aftereffect of the Thresher’s demise was the creation of SUBSAFE, an enhanced safety program established to ensure future U.S. submariners would avoid the fate of the SSN 593 crew.

And to this day, no submarine passing the rigors of SUBSAFE has been lost at sea.  


Prior to Bryant’s lawsuit last year, only 19 pages of testimony regarding the Thresher inquiry had been released to the public. As a result of his action, experts and interested parties now have nearly 1,500 pages to pore over so far. The next batch of documents is due to be released in late April.

New revelations found in the declassified documents include details of an aborted dockside “fast cruise” at the shipyard before the Thresher’s sea trials. During this highly important exercise, a simulated dive is typically conducted while still tied to the pier, to test the sub’s systems. The crew runs drills to gain experience on new equipment and reconfigured pipes and valves installed during the overhaul.

“They had to stop the fast cruise after two days,” Bryant said during the recent Naval Heritage Foundation webinar. “One of the problems they had was unfamiliarity with systems.”

In one instance, the crew needed 20 minutes to find and isolate a simulated leak in one of the sub’s seawater systems, “primarily because they were not familiar with the way the valves had been distributed after the installation,” he noted.

“This was a sign that the ship’s force was not ready for sea trials,” Walsh later added. “The USN’s training infrastructure for this new class was lacking and the ship had not been issued key documentation for reference and to train with.” 

These experts say the crew couldn’t complete a lot of the planned training because equipment broke down. As a result, work requests had to be filled out and shipyard workers were on board to complete the necessary repairs.

The Thresher also underwent significant reconfigurations during its nine-month overhaul at the shipyard, including the relocation of key plumbing valves, so even sailors who had served on the sub for a while were not well-versed with the new layout. Significant changes were made to the salt water and hydraulic pumping systems, and in the ship’s control panel, as well as many other areas.

“Knowing where they (key valves) were relocated to and being able to get to them quickly was important on a deep dive, in case one or more of them needed to be opened or shut in a hurry,” Walsh said.

The sub’s chief engineering officer, Lieutenant Commander John Lyman, reportedly wanted additional training time for his department after the first scheduled fast cruise was cut short. He never got it. That exercise was supposed to last four days; a second fast cruise was only scheduled for two days.

Bryant also notes that of the 13 officers assigned to the crew, six were serving aboard their first submarine. Harvey and Garner, the Thresher’s commanding officer and second-in-command, respectively, had both assumed their positions in the middle of the overhaul and neither, according to Bryant, had served on a submarine with the type of reactor used on the Thresher.

Harvey, in addition to his experiences aboard the Nautilus and the Sea Dragon, had also served as the engineering officer aboard the nuclear-powered USS Tullibee, which featured a hull form similar to the Thresher’s. However, the Tullibee was only built to dive about half as deep as the Thresher, and to run half as fast. The Thresher’s test depth has been reported as roughly 1,300 feet – previous subs were built to dive 700 feet.

Bryant and his colleagues are careful not to place blame on the Thresher’s sailors.

“The crew was a super-excellent crew,” said Bryant, who served aboard three Thresher-class submarines during his own Navy career, “but they didn’t have a chance to get up to speed.”


Researchers have also pointed to the Navy’s urgency in getting the Thresher out to sea to face the potential threat of Soviet submarines being developed at the time. They suggest this pressure may have curbed a more thorough review of potential deficiencies such as silver brazed joints which might have been faulty. Remember, the Cuban Missile Crisis had just six months before SSN 593 departed on her final cruise.

“They were pushing to get that submarine out,” Bryant noted.

This pressure to return the Thresher to service has long been a topic of discussion among surviving family members, who consider their loved ones “casualties of the Cold War.” Debby Ronnquist, whose husband Julius “Buddy” Marullo Jr. was a quartermaster on the Thresher, has never forgotten a discussion he and some shipmates had around their kitchen table one night shortly before their fatal dive.

“I do remember the concern in their voices and the general mood as being very worried about the readiness of the boat,” she recently recalled.

Ronnquist, now a York, Maine, resident, also emphasized that Buddy underwent “extensive training” during his dozen years in the Navy, which included service during the Korean War. “The men had to learn about all the systems, not just their own specialty.” 

But at a time when the U.S. was in a race for technological advantage over the Soviet Union, firmly believing the survival of the nation was at stake, improvements were constantly being implemented.

“What you have is a sudden need for training which is not met,” author Norman Friedman said during the webinar. “I don’t know if anyone anticipated just how dangerous that was going to be.”

This element of time apparently carried over into sea trials as well, according to Bryant. For instance, a previous practice for deep dive tests had been to submerge about a hundred feet at a time, he noted, and to check the sub’s systems at each increment before proceeding to the next depth.

The Thresher did not follow this pattern, Bryant said, but rather dove hundreds of feet at each interval. “If they had just taken a little more time and they’d found the problems before the problems found them, they might have survived that,” he said.

This may have also been due to some overconfidence in the prowess of the Navy’s nuclear-powered fleet, to the point where it was considered unlikely anything could go wrong. The Navy was especially proud of the Thresher and its capabilities.

“Remember how reliable nuclear power had proven up to this,” Friedman pointed out. “It never broke. You never heard about a nuclear sub that had lost power and had to come home on a diesel engine that it had as a backup.”

There was a bit of a swashbuckler mentality in those days prior to the disaster, in a country still flushed with victory in World War II and caught up in the excitement of the Atomic Age. Astronauts were blasting into space on rockets, and nuclear submarines were accomplishing feats unimaginable during the wartime-era of diesel subs. Things were happening fast – maybe a little too fast.

The Navy didn’t fully appreciate the risks involved in developing a submarine which nearly doubled the test depth of previous subs, according to both Bryant and Walsh, who spent nearly four decades working for the Navy Department and is now a Laconia-based consultant.

After the loss of the Thresher, the Navy included more time for operational training during overhauls.  But these experts, all well-versed in the lore of American submarines, emphasize the tragedy resulted from numerous developments, big and small.

“Certainly, crew training was a key contributing cause,” said Walsh, “but it wasn’t the only one.”

D. Allan Kerr is the author of Silent Strength, a book about the men lost aboard the Thresher.

(April 6, 2021)

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