Peter Jackson’s World War I documentary “They Shall Not Grow Old” earned $2.3 million at 1,142 theaters in North America on Monday.

Warner Bros. released the movie five weeks after it aired on Armistice Day on the BBC. The studio partnered with Fathom Events in the U.S. for a one-day event, marking the largest single night for a Fathom documentary, a spokesman said.

Fathom — which specializes in event cinema and is jointly owned by AMC, Cinemark and Regal — will show “They Shall Not Grow Old” at about 800 locations for two shows on Dec. 27. Warner Bros. will launch a theatrical release in New York, Los Angeles, and Washington, DC, on Jan. 11 and plans to expand to 25 markets on Feb. 1.

Jackson began developing the project in 2014 and decided to use the voices of the actual British soldiers and colorize actual footage from World War I. The film was commissioned by 14-18 Now, the U.K. arts program for the First World War centenary, and the Imperial War Museum, in association with the BBC.

“We thought the only people we should hear were the ones who fought the war,” he noted at a screening on Dec. 7 at the Linwood Dunn Theatre in Hollywood. “The BBC had recorded a lot of guys in the ’60s and we had 600 hours of interviews. So you’re going to hear the voices of 120 men.”

Jackson also culled the World War I footage from 100 hours that were in the archives of the Imperial War Museum. It’s estimated by historians that nearly 20 million soldiers and civilians perished during the war, which began in 1914 and ended on Nov. 11, 1918.