The Titanic is one of the most famous shipwrecks on the seafloor, but for decades following the 1912 disaster, its debris remained undetected. It took a secret Cold War Navy mission to find two unrelated vessels to finally pinpoint the doomed ship's location.

Now, the history of the Titanic's discovery is the subject of “Titanic: The Untold Story," a new exhibit at the National Geographic Museum in Washington D.C. In 1985, U.S. Navy commander and National Geographic Explorer-at-Large Robert Ballard was commissioned by the Navy to use a submersible to find the wreckage of two nuclear submarines. The USS Thresher and the USS Scorpion both went down in the North Atlantic Ocean during the Cold War, and the U.S. government wanted to know why the ships sank, as well as what impact their nuclear reactors had on the environment.

Ballard agreed to help, but he had a request of his own: He wanted to use the submersible technology to search for the remains of the Titanic, which he suspected ended up in the same area as the submarines he was asked to investigate. He received permission to pursue the side project, just as long as he completed the primary mission.

After tracking down the Cold War submarines, Ballard and his crew launched their own mission to find the Titanic using historical records detailing where the ship may have sunk and where the lifeboats were rescued. They received the first images of the sunken ship's boiler, something last seen when the Titanic was above water, on September 1, 1985.

The previously classified story is told in detail at the National Geographic exhibit, which is now open to the public through January 6, 2019. The show will also feature artifacts from Titanic history, like a deck chair and sheet music that belonged to Wallace Hartley, the bandleader who insisted on playing as the ship sank.

[h/t National Geographic]