TOKYO (Kyodo) -- Aerial warfare historian Yusuke Orita was thrilled when his decade-long effort to collect and analyze U.S. military war film footage led him to uncover a rare color segment showing Japan's famed battleship Yamato under attack in 1945.

As the task of passing down memories of World War II becomes more difficult after 80 years, the 39-year-old believes that carefully examining archival sources -- often left undated and unattributed -- can help bring new dimensions to the understanding of warfare.

"I hope it will serve as a tool for people to understand the reality of war," Orita, a member of a civic group studying local history in Usa, Oita Prefecture, said during a recent phone interview with Kyodo News.

Since 2012, the group, named Toyonokuni Usashijuku, has obtained copies of Pacific Theater footage filmed by the U.S. military from the U.S. National Archives. By cross-referencing the clips with Japanese and U.S. documents and other sources, they have worked to pinpoint exactly when, where, and what was captured.

As of July this year, its collection includes 336 videos, about 54 hours in total, filmed using methods including cameras mounted on U.S. fighter aircraft between August 1943 and October 1945.

The footage covers over 400 locations, primarily in Japan but also in 10 other countries and regions.

So far, the most memorable archival discovery for Orita is the color footage of the Imperial Japanese Navy's Yamato, the largest battleship ever built, sailing off the coast of Iwakuni, Yamaguchi Prefecture, on March 19, 1945.

"I finally found the Yamato in motion (in color)," Orita recalled in the interview, adding he did not recognize the massive ship at first sight because of the poor quality of the clip but that the vessel's high-speed maneuvering gave it away.

The footage, shown to the public last year, depicts the Yamato being attacked from the air and maneuvering between columns of water.

Less than a month later, the heavily armed ship, which took part in the battles of Midway and other operations, was sunk off southwestern Japan by hundreds of Allied plane attacks.

In the late stages of the Pacific War, Japanese cities had been frequently bombed by the U.S. military, which had established air superiority.

Analyzing wartime footage can shed light on historical details absent from official documents and provide a vivid way to understand events.

One example Orita cites is the Jan. 9, 1945, U.S. bombing of a Japanese ship carrying Allied prisoners of war, often referred to as a "hell ship" due to the conditions on board, while it was anchored in present-day Kaohsiung Harbor in Taiwan.

The U.S. military in the aftermath of the attack recorded it as a successful attack on Japanese shipping but it immediately killed approximately 330 Allied POWs who were on the ship bound for mainland Japan, Orita said during a press briefing at the Foreign Press Center Japan in July.

A different video clip, meanwhile, offers a clue as to why the U.S. military strafed many schools during air raids on Japan, attacks often criticized as inhumane.

The footage shows a school building under attack in Oita Prefecture on July 31, 1945, despite efforts to camouflage it. Ironically, Orita suggests, the camouflage may have drawn attention: a U.S. report noted that what appeared to be military barracks had been strafed.

Orita, who is also a city official of Usa, said his interest in World War II began in elementary school after noticing a gap between what he learned at school and how his grandfather remembered the war.

"He was very nostalgic about the war, while also carrying a sense of guilt toward his peers who died," said Orita, explaining that it was a contradiction that he could never fully grasp.

As a high school student Orita was drawn to journals and memoirs of people who fought on the battlefields and dreamed of one day analyzing gun camera footage himself.

Orita has now spent some 15 million yen ($100,000) to gather footage and official documents.

Orita's search for Pacific war archives has expanded beyond the U.S. National Archives to include U.S. universities, museums, and potentially materials kept at the Japanese National Institute for Defense Studies.

In September, he visited the National Museum of the Pacific War in Fredericksburg, a small town in Texas with a population of around 10,000, having learned that they have footage and photographs on the war. He also delivered a lecture there, showing some footage he has analyzed.

Orita believes his video analysis will only gain significance as Japan faces a transition period in terms of how to keep alive the memories of the war for the next generation, with fewer chances to directly hear testimonies from witnesses.

"Memories of the war were passed down mainly through testimonies of living people. But we need to shift to an approach that largely relies on historical materials," he said, arguing that visual information will play a key role in the process.