A sunken Soviet submarine packed with nukes.  A window for America to gain the upper hand in the Cold War. A CIA cover story worth $3 billion. I give you Project Azorian, or how the U.S. tried to steal a Soviet sub.

It’s the late 1960s.

Nuclear submarines are a key cog in a country’s deterrence capability. ICBM silos could be located or betrayed. But a sub slithering through the cold oceans ensures that no strike would ever go unavenged.

March 1968 — North Pacific Ocean.

The Soviet Pacific Fleet scrambles into action. K-129, a patrolling Golf II nuclear submarine, carrying three nuclear ballistic missiles and two nuclear torpedoes has just sunk, some 2,000 miles northwest of Hawaii.

The fate of her crew, but more importantly of her classified arsenal, cryptographic devices, and codebooks, is on the balance. The Russians go all in. Nothing. Despite a vast search-and-rescue operation, two months pass with no results.

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The unfortunate K-129. She went down with all hands after an internal explosion (CIA.gov).

The task force retreats to its base.

A prying CIA senses an opportunity. Surely, they argue, the Soviets have just lost a nuke sub. Nothing else would explain such an uncommon activity. (Interestingly, a network of hydrophone listening stations, called Sound Surveillance System (SOSUS), traversed (and still does) the American coasts, ever vigilant for any unnatural noise that could result in an intelligence coup.)

It’s now time for the U.S. Navy to try where the Soviets failed.

USS Halibut, a special-operations-capable sub, sails from Pearl Harbor. Fitted with Fish, a 12ft-towed Remotely Operated Vehicle (ROV) packed with cameras and sonars and designed for such delicate missions, USS Halibut sets off to locate and photograph the wreck.

With a search area of around 1,200 square miles, it won’t be easy.

USS Halibut had to cover huge swaths of water to locate K-129 (Wikipedia.org).

Weeks pass to little avail. And then success: USS Halibut manages to find the exploded K-129. After taking thousands of pictures, she sails back to Pearl Harbor. For her success, USS Halibut receives a classified Presidential Unit Citation. It won’t be the last.

Now, with the wreck discovered, it’s time to retrieve it.

But how?

With K-129 resting more than three miles at the bottom of the ocean, the technology to retrieve any codebooks or cryptographic machines, nevermind the humongous nukes, doesn’t exist.

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And even if the technology existed, how could the U.S. mask such a gigantic operation from the Soviets?

Enter Howard Hughes, billionaire extraordinaire and frequent cover man for the military’s and CIA’s covert programs.

It is 1969. The CIA approaches Hughes with a novel proposal:  Build, they tell him, a salvage ship to which we’ll attach a heavy-duty mechanical claw and winches to grip the sub and lift it!

Hughes agrees.

The Hughes Glomar Explorer (HGE), a 619ft-long deep-sea mining vessel, which includes a derrick, docking legs and wells, and a huge mechanical claw to hoist the wreck, takes four years to build; her unique equipment was installed under complete secrecy.

The Hughes Glomar Explorer, one of CIA’s most costly schemes (Wikipedia.org).

President Nixon, with the blessings of Henry Kissinger and William Colby, (Director of Central Intelligence), orders the operation to commence.  He first has to wave off concerns from some military and intelligence officials who, despite the enormous funds already invested, question K-129’s potential benefits so many years after its sinkage.

Under the cover story that she’ll be searching for manganese-rich veins to mine, Glomar Explorer sets sail from Long Beach, California. Her special devices mean that the whole recovery can be made underwater, thus fooling the expected Soviet reconnaissance.

She arrives at the wreck and begins the salvage operation. Keeping her company are two Soviet surveillance ships.

For the better part of a month, the Glomar Explorer’s crew toils to hoist K-129’s wreck.  And with the sub almost up, disaster strikes: K-129’s eroding hull tears under the strain of the recovery process and breaks apart. Only a section of it remains gripped in the Glomar Explorer’s mechanical claw.

Under President Ford — Nixon has just resigned over Watergate — the White House contemplates a second recovery attempt. But, after a series of events that included a stolen document linking Hughes with the CIA, the press breaks the story (Colby unsuccessfully tries to halt the publishing).

No second attempt is to be made.

And thus ends one of Cold War’s more interesting intelligence operations.

What was recovered from inside K-129’s hull remains classified. Rumors have implied that a couple of nukes and some codebooks were salvaged. But this is just speculation. A heavily redacted CIA document released in 2010 said that so far “much fact and extensive error” has been published.

The whole truth remains hidden in a dusty CIA vault.

To this day, K-129’s exact location remains classified.