This post has been substantialy revised and rewritten.

Memorial Day is the most heart-breaking of holidays.

One way to better grasp war’s tragic cost is to watch director Peter Jackson’s extraordinary documentary, "They Shall Not Grow Old.” (You can rent it on YouTube, Apple TV and Prime) Working with century-old film footage and the recorded interviews of more than 100 veterans, Jackson vividly resuscitates the young soldiers of World War I.

Millions of young men died in the brutal trench warfare of the Great War, and this film manages to supply texture and layers of detail to that real Lost Generation. For the war had been launched with great exuberance, as young men of all social classes rushed to enlist in a “jolly little war” that was sure to be over soon. The brutality and carnage, however, went on for four years.

The film is able to vividly capture all this because Jackson’s team spent years restoring badly damaged footage from the Imperial War Museum’s archives. They retooled the hand-cranked film stock to run at modern movie speeds and then pumped life into it with color.

I am generally no fan of colorizing vintage black-and-white celluloid. But here it enables you to see the immense amount of youthful vitality, energy and joy lost in the quagmire of World War I -- indeed, in all wars.

The soundtrack comes from hundreds of hours of interviews conducted with WWI veterans, describing life on the Western Front. Jackson dazzlingly matches words to images as the war unfolds. Their excitement and exhilaration at the start in 1914 and their dazed horror by the end in 1918 is evident for all to hear.

Be sure to watch through the final credits to hear a raucous, raunchy rendition of “Mademoiselle From Armentières,” which runs as the names of all the soldiers interviewed scroll by. As Jackson explains in a short film about the making of his documentary, they had essentially run out of money, so he asked the staff of the local British Consulate to come sing the song. Their vitality makes the tragic cost of war even more searing.

Jackson’s film reminds me of one of the best Memorial Day opinion pieces I've read. “War Immemorial” is by Gardner Botsford, a legendary New Yorker editor who was a World War II vet. In his wonderful memoir, “A Life of Privilege, Mostly,” Gardner’s wartime activities seem almost charmed – he keeps running into old school pals as the American G.I.’s advance toward Paris. (He also describes The New Yorker he worked on as “the Hollywood version of journalism” – more rollicking, with fascinating people engaged in larger-than-life escapades.)

Botsford’s Memorial Day piece, however, demonstrates he well understood the terrible price of war. For he emphasized that the overarching loss is the lives not lived by these millions of young people:

"The most powerful Second World War memorial I know is not really a memorial at all, and the memory it preserves is not decked out with 56 granite pillars or a waterfall. It is the cemetery on top of the bluffs overlooking Omaha Beach, in Normandy. Acre upon acre of stark white crosses and Stars of David. Row upon row of graves, reaching almost out of sight. … It is the kind of place where you take off your hat without thinking. So many and so young, still in their teens and 20's. They would be in their 80's now, or almost, and who knows what they might have done with themselves. Possibly nothing, probably nothing extraordinary. It doesn't matter. They are truly memorable now just as they are."

Earlier this month, I took a walking tour of the World War 1 memorials in New York’s Central Park. There is one lovely area where trees had been planted soon after the Great War in memory of some of the young New Yorkers who had been killed. A small stone plaque had been placed in front of each tree, with the name, dates and military rank of the soldier being honored. Now, however, more than 100 years after the war, most of the trees have died. Only the plaques remain.