Just when you thought there couldn’t possibly be anything new to learn about the Civil War, Ric Burns’s must-see “Death and the Civil War” arrives. This isn’t battles and generals but rather the painful, often avoided subject of the gruesome deaths of the ordinary soldiers who were killed by the hundred thousands and what happened to their remains. Or maybe we should say, what didn’t happen to their remains.

“Death and the Civil War” premieres Sept. 18 from 8 to 10 p.m. on the PBS series “American Experience” and is an important addition to the ongoing discussion of the war on its sesquicentennial.

The film, based on Harvard University President Drew Gilpin Faust’s book “This Republic of Suffering: Death and the American Civil War,” adds a visual component to that landmark tome.

The country was not prepared for war, either in the North or South. No one believed it would be a long war, and so no one planned much beyond three months. But as the years passed, the lack of military preparedness to handle the battle dead as well as those who died of disease became a critical problem. Burns shows us many rarely seen photographs of the dead on the battlefield, the bodies lined up in long rows for mass burials or, worse, not buried at all.

There was no system for notifying family, adequately marking burial sites or even keeping accurate records of who had died. There were no national cemeteries.

Burns is an imaginative story-teller who does not allow the film to be nothing but another depressing documentary. Instead, he concludes with a celebration of the American can-do spirit. Ordinary people recognized the problems and did something about it, such as Clara Barton, who spent several years after the war accounting for the Union war dead, something the federal government had not done. In the South, a group of African Americans saw the need to treat all dead soldiers with dignity and created their own cemetery and gave each of those who had died in their area a proper burial.

This is a film to watch. “Death and the Civil War” will be a much talked-about documentary, one that deals with the war from a different angle and does it extremely well.