New Declassified Documents Reveal the Truth Behind the USS Thresher Sinking

Back in 1963, a U.S. Navy submarine called the USS Thresher sunk, taking the lives of 129 crew members aboard. What exactly had happened to the craft remained a mystery for years, until a retired Navy submarine commander called James Bryant won a lawsuit in 2020, forcing the service to release its reports on the event.

Since then, more files have been declassified that show that the Navy was not covering up the accident. The files prove instead that there was no single event that led to the ship sinking. 

"The following is the fifth release from the Navy related to the FOIA [Freedom of Information Act] suit. While the prior releases were proceedings of the 1963 court of inquiry following the 1963 loss of the attack boat, this release is the previously unclassified 1978 two-volume history, Sea-Based Airborne Antisubmarine Warfare 1940-1977," the U.S. Naval Institute’s online news and analysis portal wrote in a statement as they unveiled the document. 

"The document was part of Bryant’s original FOIA request. The so-called Cross report was declassified in 1990 and mentioned the original test depth of Thresher in passing as part of a short history of U.S. and Soviet 1960s era nuclear submarine programs," it continued. 

The USS Thresher was a nuclear-powered attack submarine which means it could stay underwater indefinitely and didn’t require a hull shape for sailing on the surface. So what happened to it exactly?

On April 9, 1963, the ship was undergoing diving tests 220 miles (354 km) east of Cape Cod. The submarine then reported it was suffering “minor difficulties” and it would return to the surface. But it never did.

The navy later found the ship broken up into six different pieces at the bottom of the ocean with all on board dead.

According to the panel of experts, the causes are as follows. First, the Navy rushed to get the Thresher into the fleet, and it seems that the crews of these new vessels were inadequately trained. Second, the crews were too overconfident in the systems and didn't think that nuclear-powered submarines could lose power. Third, and perhaps most importantly, improper welded caused the piping to rupture on the ship, which caused a leak that shorted the ship’s electrical system. 

Crews couldn't reach equipment to stop the flooding, the ballast tanks didn't work as they should, and the improperly trained crew just made everything worse. 

So, it seems that this seemingly mysterious event has a rather everyday explanation. Contrary to popular thought, there was no actual cover-up. Rather, the Navy kept the event (and the documents) secret to prevent the release of operational details that may have benefitted the country's enemies.

Disclaimer: This article has been updated to add more information regarding the nature and cause of the sinking.