A bronze bell has been recovered from a Japanese submarine that was sunk intentionally off the Hawaiian Islands by U.S. forces 70 years ago.

Researchers from the Hawai'i Undersea Research Laboratory (HURL) in two submersibles, Pisces IV and Pisces V, used a robotic arm to retrieve the bell that was resting on the seafloor.

The bell was from the I-400 - a World War II-era Imperial Japanese Navy mega-submarine, lost since 1946. Longer than a football field at 400 feet, the I-400 was known as a "Sen-Toku" class submarine - the largest submarine ever built until the introduction of nuclear-powered subs in the 1960s.

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"It was an exciting day for the submersible operations crews of Pisces IV and Pisces V,” Terry Kerby, HURL operations director and chief submarine pilot, said in a statement.

Kerby said that Georgia Fox, an archaeologist at California State University-Chico, had just received an underwater archaeological research permit from the Naval History and Heritage Command. “We had only one chance to relocate and recover the bell," Kerby said.

At the end of World War II, the Navy captured five Japanese subs, including the I-400, and brought them to Pearl Harbor for inspection. When the Soviet Union 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 the coast of O'ahu.

The Americans wanted to keep their advanced technology out of Soviet hands. Since then, HURL has successfully located four of these five lost submarines.

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"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 re-shaped the Pacific region," said Hans Van Tilburg, maritime heritage coordinator for NOAA in the Pacific Islands region. "Wreck sites like the I-400 are reminders of a different time, and markers of our progress from animosity to reconciliation."

Following a year-long stabilization process, the bronze bell will be on display at the USS Bowfin Submarine Museum, where it will join binoculars and other artifacts from the I-400.

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"The recovery of the bronze bell from the I-400, and its eventual display at the USS Bowfin Submarine Museum gives us a chance to share this history with more than three hundred thousand annual visitors, many from the Pacific Region,” Jerry Hofwolt, executive director of the USS Bowfin Submarine Museum, said. “What was once an artifact on the seafloor will now be a national historic maritime treasure for all to see."