Mikhail N. Panin's "Secret Departure of Ivan the Terrible before the Oprichnina"

A massive 19th century oil painting of Ivan the Terrible, the first czar of Russia, was returned to its rightful owners on Monday, after its disappearance from a Ukrainian museum more than 75 years ago during World War II.

The Ukrainian ambassador to the U.S., Valeriy Chaly, accepted the painting on behalf of the people of Ukraine during a repatriation ceremony at a fine arts auction house outside of Washington, D.C. He called its return a "demonstration of unity and solidarity with the Ukrainian people."

"The damage from the theft of this painting really cannot be quantified," said Jessie Liu, U.S. attorney for the District of Columbia. "There are generations of people who weren't able to see this painting ... We hope that the repatriation of the painting is the first step in remedying that harm."

Get Breaking News Delivered to Your Inbox

In 1941, Nazis looted Mikhail N. Panin's "Secret Departure of Ivan the Terrible before the Oprichnina" from the Dnepropetrovsk Art Museum during Germany's occupation of Ukraine. The 64-square-foot painting portrays the Russian czar fleeing the Kremlin on horseback.

David and Gabby Tracy screenshot from SKYPE

Gabby and David Tracy purchased a home in Ridgefield, Connecticut, in which the large painting conveyed with the property in 1987. Unaware of the painting's history, the Tracys enjoyed the painting until 2017, when they decided to downsize and auction the artwork.

As the painting was being prepared for auction, an employee of the auction house, Potomack Company, discovered the artwork's true origins, which were later confirmed in an email sent by the director of the Dnepropetrovsk Art Museum.

"Attention! Painting 'Ivan the Terrible' was in the collection of the Dnepropetrovsk Art Museum until 1941 and was stolen during the Second World War," the email read. "Please stop selling this painting at auction!!! According to the international rules of restitution of stolen works of art, the picture should return to Ukraine."

It's hard to imagine this could have come as a greater surprise to Gabby Tracy, a Holocaust survivor, whose own father died in a concentration camp. She lived in a Jewish ghetto in Budapest until the Soviet liberation. Tracy eventually fled to the U.S. as a refugee with her sister and brother in 1947.

"We're very happy to give it back to the Ukrainian people, and I hope one day we go there and see it hanging in the [Ukrainian] museum," she said via Skype during the repatriation ceremony.

The stolen property was never auctioned. It was seized by the U.S. government under forfeiture law with full cooperation from the Tracys. A subsequent FBI investigation uncovered additional proof of the painting's origins, including black and white images of the art hanging in the Ukrainian museum around 1929.

"Art crime is one of the FBI's lesser known priorities, but it is an important one given the cultural implications," said FBI special agent Timothy Dunham. He added, "I think [Mrs. Tracy] found it very rewarding to be a part of something like this — returning stolen property."

The FBI says it has returned about 15,000 items of cultural significance since the formation of the FBI's Art Crime Team roughly 15 years ago.

According to one estimate by the National Archives, Nazis looted 20% of Europe's art during World War II.