Updated

Korean battle flags purportedly connected to Kim Ung-u, a direct ancestor of Kim Jong Un, were found this month at the U.S. Naval Academy, the U.S. Naval Institute (USNI) said Friday.

Workers had been opening display cases for the first time since 1920 to remove British flags, according to the institute in Annapolis, Maryland. “Staff from the Naval Academy Museum found several dozen flags hidden behind the framework including the Korean standards that are still vivid.”

It's likely the flags were kept behind other items on display because there just wasn't enough space to show them all, officials said.

NORTHKOREA-MISSILES/DIPLOMACY

The flags have been tied to Kim Ung-u, an ancestor of North Korean leader Kim Jong Un (pictured). (KCNA/via REUTERS)

The USNI said the USS General Sherman, a merchant ship, went to Pyongyang in 1866 to try opening the country to trade - but Koreans, believing the ship’s purpose was to loot temples, murdered the crew and set the ship ablaze.

NORTH KOREANS MARK 6TH ANNIVERSARY OF KIM JONG-IL'S DEATH

“The incident is still celebrated in North Korea as a strike against American imperialism with the claim that Kim Ung-u, a direct ancestor of Kim Jong Un, planned and led the attack though there is no historical evidence of his involvement,” the institute explained.

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A North Korean postage stamp depicting the attack on the USS General Sherman. (USNI News)

Kim Ung-u was the great-great-great-grandfather of Kim Jong Un, North Korean officials said.

Five warships from the U.S. moved toward Korea’s coast in 1871, seeking to ask about what happened to the other ship and set up diplomatic relations, USNI says. The Koreans fired before the “U.S. Marines captured several coastal forts and removed the flags.”