The find was front page news, just as the original disaster had been. In September, 1985, the New York Times proclaimed: “Wreckage of Titanic Reported Discovered 12,000 Feet Down.” The famous ship’s remains were found at the bottom of the ocean by “a team of American and French researchers,” the paper reported, later clarifying that American researchers were scientists from the Woods Hole Oceanographic Institution.

But over 30 years later, the marine geologist behind the discovery has revealed the truth about his now-declassified expedition: it was part of a secret U.S. military mission to recover two sunken nuclear submarines from the sea floor. ”They did not want the world to know that, so I had to have a cover story,” Robert Ballard told CNN. Details of the true story are now on display at Washington, D.C.’s National Geographic Museum until the end of the year.

While it is true that a team from the Woods Hole Oceanographic Institution found the Titanic, what was not reported at the time were the conditions put in place by the U.S. Navy—or their involvement with the mission at all. Ballard was not exclusively a Woods Hole Oceanographic Institution scientist, but also a U.S. Navy Commander. The navy would fund the mission, CNN reported, but only if Ballard first explored the USS Thresher and the USS Scorpion, two American nuclear subs that had sunk about 20 years prior.

“We knew where the subs were,” Ballard told CNN. “What they wanted me to do was go back and not have the Russians follow me, because we were interested in the nuclear weapons that were on the Scorpion and also what the nuclear reactors (were) doing to the environment.”

By the time the researchers had finished exploring these two nuclear subs, however, there were just 12 days left to find the Titanic. Its discovery, more than 12,000 feet below the ocean’s surface, was an incredible victory: ”When we found the Titanic, we naturally were very excited, because it was a tough job. We got it, scoring the winning goal at the buzzer.”

Ballad later attempted to suppress the wreck’s precise coordinates, but they were leaked, resulting in multiple treasure hunters visiting the site, salvaging thousands of objects and leaving a trail of destruction in their wake. Since 2012, the wreckage has been protected under the UNESCO Convention on the Protection of Underwater Cultural Heritage. But while humans have backed off, the ocean has been working uninterrupted to dismantle the ship’s remains.