The Hawaii Undersea Research Laboratory has retrieved a bronze ship’s bell from the World War II Japanese I-400 mega-submarine that was sunk in 1946 off the southwest coast of Oahu.

Longer than a football field at 400 feet, the airplane-carrying I-400 was the largest submarine ever built until the introduction of nuclear subs, the University of Hawaii said.

The undersea research lab, or HURL, is part of UH’s School of Ocean and Earth Science and Technology. The diesel submarine was discovered in August 2013 by the lab in more than 2,300 feet of water off Barbers Point.

UH said the bell recovery was made during a test dive this month using both of the research lab’s submersibles, Pisces IV and Pisces V, and led by veteran undersea explorer Terry Kerby, operations director and chief submarine pilot.

The research lab has located four of five Japanese submarines that were brought to Pearl Harbor after the war.

“These historic properties in the Hawaiian Islands recall the events and innovations of World War II, a period which greatly affected both Japan and the United States and reshaped the Pacific region,” Hans Van Tilburg, maritime heritage coordinator for the National Oceanic and Atmospheric Administration’s maritime heritage research effort in the Pacific, said in a news release.

“Wreck sites like the I-400 are reminders of a different time, and markers of our progress from animosity to reconciliation,” Van Tilburg said.

Following a yearlong stabilization process, the bronze bell will be on display at the USS Bowfin Submarine Museum, along with binoculars and other artifacts from the I-400, UH said.

A survey dive last year with NHK, Japan’s largest broadcasting organization, turned up the bell, which had been torn from the submarine by the explosive force that broke apart and sank the massive vessel.

The I-400 and I-401 submarine aircraft hangars were each capable of holding three folding-wing floatplane bombers that could be launched by catapult with each carrying an 1,800-pound bomb, UH said.

Former Navy Lt. Cmdr. Allen B. “Buck” Catlin recalled in 2008 how he helped bring five Japanese subs to Pearl Harbor after the war: the I-400, I-401, I-14, I-201 and I-203.

The U.S. Navy boarded at least 24 Japanese submarines at war’s end, but to keep the technology out of the hands of the inquisitive Soviet Union, most were loaded with explosives and sunk off Nagasaki, Catlin said.

When the Soviets demanded access to the submarines in 1946 under the terms of the treaty that ended the war, the U.S. Navy sank the subs off Oahu and claimed to have no information about their exact location, UH said.