One thing that makes a film a “classic” is how modern it feels, no matter what decade produced it.

By that measure, William Wellman’s “The Story of G.I. Joe” (1945) is the “Citizen Kane” of combat dramas, the “Saving Private Ryan” of its day.

Wellman & Co. may have shot many scenes on soundstages and used rear projection to fake driving sequences. But this North Africa/Italian Campaign grunts-eye-view drama feels real, lived-in, with little in the way of heroics or melodrama. With its mud and rain, authentic ruins and realistic firefights, it doesn’t look like any contemporaneous combat film. And within a couple of years, the entire genre would bend towards imitating this version of many an America’s World War II combat experience.

Director “Wild Bill” Wellman (“A Star is Born,” “The Ox Bow Incident”) earned his nickname as a French fighter pilot during World War I. But “G.I. Joe” gently mocks the “glamour boys” of the Air Corps, and presents infantrymen as its inspiration — the Pulitzer Prize winning war correspondant and columnist Ernie Pyle — saw them, in their element.

“It was chaos, indefinable,” Pyle wrote, in voice-over narration performed by the great Burgess Meredith, who plays him in the film, with “each boy facing the worst moment of his life — alone.”

Pyle might be in a quiet but fraught forward command post as the first major American battle of the North African campaign — Kasserine Pass (unnamed) — goes wrong. But his bread and butter was embedding with a platoon, seeing what they saw, experiencing what they did, a “little guy,” over 40 who “doesn’t have to be here” giving these other littleguys a voice in the pages of America’s newspapers.

“Hey Ernie, tell Cleveland Joe McCloskey’s winning the war single-handed!”

The script, by three credited writers, can sound like overheard foxhole conversation, with Pyle listening in, maybe taking notes, and typing out dispatches adorned with authentic G.I. speak.

“You know, when this war’s over, I’m gonna buy a map and find out where I’ve been.”

The G.I.s depicted here may look the way movie soldiers did back then, played by actors older than the “boys” they’re meant to portray. But they are three dimensional human beings — flawed and petty, noble and heroic, stoic and grumpy.

“If this war don’t kill me first, my feet will.”

And Pyle was their poet laureate, relating the lives they left behind and the life they might very well lose to worried and empathetic “folks back home.”

“For those beneath the wooden crosses, there is nothing we can do, except perhaps to pause and murmur, ‘Thanks pal, thanks.'”

We meet Pyle as he joins up with a green infantry platoon let by Lt. Walker (a very young Robert Mitchum, hard and charismatic as hell) in a combat zone that looks little like Algeria or Tunisia (So.Cal. locations, of course).

Pyle, like the soldiers whose experience he is documenting, will learn to travel light, to sleep on the shovel he dug his foxhole with. He will watch Walker age into a man hardened by death and inadequate rations and sleeplessness and misery as he is promoted captain. Pyle will see the G.I. whose fiance became a combat nurse to be near him treated to a G.I. field wedding. And he will watch Sgt. Warnicki (Freddie Steele, a standout in the cast) hunt all over Italy for a Victrola that will play the record his wife back home made with the voice of the son he’s never met.

And Pyle will take on his share of the responsibilities of looking after the North African mutt the guys name “Ay-rab” and adopt as a mascot, which Lt. Walker orders them to ditch until “the press” shows up.

Walker gets it. Only draft dodgers with bone spurs hate dogs. That won’t look good in print.

There are plot elements and characters that were combat cliches before “The Story of G.I. Joe,” but Wellman treats it all with a dogged determination to grimy everything up so that this all feels documentary real — burning tanks, battered Jeeps, soaked, stubbled and bloodied soldiers.

Battles and place names are left out as Pyle follows this fictional corps from North Africa and the Kasserine Pass to Monte Cassino and the road to Rome.

As the firefights pass by and the stalemate at Monte Cassino kill some and wear on all, we’re set up to sense something tragic is coming, with the only mystery being who it will happen to, and when. Yeah, the Lt. growls, “the first death’s always the worst,” a nameless G.I. killed in a random bit of strafing. But every death here will sting, especially the final one.

Perhaps the most modern thing about “G.I. Joe” is the fact that Wellman knew this world and this story and these emotions well enough to know when to drop the mike. The film finishes with that death, and well before the war is over, months before these men and Pyle know if they will survive this theater of action and then be sent to the Pacific.

The film came out in the summer of ’45, before Hiroshima and Nagasaki. The war’s outcome was no longer in doubt, with just the final death toll to be determined, who would survive and who wouldn’t.

So Wellman ended his film without music, without credits, without one second of flag waving. He just had to hope Ernie Pyle would approve.

Rating: TV-PG, violence, combat, sexual situations, smoking

Cast: Robert Mitchum, Burgess Meredith, Freddie Steele, Wally Cassell, Jimmy Lloyd, William Murphy and John R. Reilly.

Credits: Directed by William Wellman, scripted by Leopold Atlas, Guy Endore and Philip Stevenson, based on the writings and career of Ernie Pyle. A United Artists release, restored and on Tubi and available from Ignite Films.

Running time: 1:48