StarSolidStarSolidStarSolidStarOutline(3 stars)

Spike Lee’s new movie, “Da 5 Bloods,” arrives at a time when the director’s singular voice couldn’t be more needed. In a rousing, gorgeously modulated prologue that we’ve come to expect from a Spike Lee Joint — this one offering a whirlwind tour of the protest movements of the 1960s and the violent pushback they received from government and law enforcement — it looks as if the 63-year-old director has made another film that uncannily meets its moment. If the ensuing, relatively conventional, drama doesn’t always live up to that early promise, its moments of stinging insight and soaring cinematic rhetoric once again prove why Spike Lee might be America’s most indispensable filmmaker.

Case in point: The seamlessly graceful transition from that electrifying opening montage to the present day, when four Vietnam veterans gather in a fancy Ho Chi Minh City hotel for a reunion and a mission. Eddie — a wealthy car dealer played by Norm Lewis — is treating his buddies to the trip, on which they intend to recover the remains of their squad leader. As they embrace and give each other the business, snippets of their characters emerge: Otis (Clarke Peters) is watchful and reserved; laid-back Melvin (Isiah Whitlock Jr.) works on keeping it mellow; and Paul (Delroy Lindo) possesses the kind of taut, tightly coiled energy that could go off at any minute. (He also happens to be a proud Donald Trump supporter: In “Da 5 Bloods,” the villains wear a red hat, not black.)

The group obeys all of the conventions of war pictures of yore — the strategizer, the quiet one, the clown, the hothead — and that includes the man they are trying to find: “Stormin’ ” Norman, played in flashbacks by Chadwick Boseman, didn’t just lead them in battle but elevated their collective consciousness about serving their country, while also disproportionately dying in a war that wasn’t their fight.

In addition to finding Norman’s improvised grave, the friends have a hidden agenda, involving a cache of gold once intended for the U.S. forces’ South Vietnamese allies. “Da 5 Bloods” owes as much to “The Treasure of the Sierra Madre” and “Three Kings” as it does to “Apocalypse Now,” which Lee exuberantly invokes in a movie that wears its influences proudly, if not always subtly. Changing up aspect ratios and mixing in 16mm film stock and iPhone footage to delineate time periods, Lee gives “Da 5 Bloods” his usual jolts of visual energy, interjecting still photographs to illustrate tutorials on everything from the brutality of the My Lai Massacre to the glory of 400-meter hurdles champ Edwin Moses.

In the hands of any other filmmaker, such didactic digressions might drag down the narrative. But Lee’s passion and fluency make them far more engaging than the putative drama of “Da 5 Bloods,” which is at its least involving when it’s at its most generically formulaic. Although he has clearly learned from the mistakes made in his starchy, unfocused World War II film “Miracle at St. Anna,” Lee still stumbles here and there when choreographing the action sequences and multiple firefights. Danny Bilson and Paul De Meo’s script, which Lee rewrote with Kevin Wilmott, is often stilted, plotty and overstuffed. One secondary cast of characters in particular has a tendency to pop up with perfunctory, unconvincing convenience.

Lee has cast some of the best character actors in Hollywood to play his title characters; Lindo especially commands the screen with a scenery-chewing performance that has madness and music at its core. (The rest of the Bloods remain frustratingly under-drawn.) But he reverts to male-gaze cliche when he enlists stunningly beautiful actresses — Mélanie Thierry and Lê Y Lan — to play the only two women in a movie that interrogates themes of greed, loyalty, self-sacrifice and the racism that led to so many black soldiers serving and dying in Vietnam, as well as masculinity itself.

“Da 5 Bloods” is most invigorating when Lee is most sharply polemical, whether it’s during that vibrant prologue, or when he stops to drop some knowledge in interstitial flashes of history, wisdom and exuberant wit. Although Lee’s frequent collaborator Terence Blanchard has written an orchestral score that swells with old-school triumphalism during the film’s most melodramatic moments, it’s the Marvin Gaye songs — all of them culled from “What’s Going On” — that serve as “Da 5 Bloods’ ” most powerful musical motif.

That 1971 album, of course, was a masterpiece, both within the context of pop music and the political upheavals of that era. “Da 5 Bloods” may go over the top in its messianic depiction of Boseman’s character, who becomes increasingly — and improbably — more Christ-like as the mysterious circumstances of his death are (unsurprisingly) revealed. But he delivers one of the film’s most memorable and powerful moments in a flashback, when he describes living in a police state back home. “Every time I walk out that door,” he says, “I can feel how much I ain’t worth.” Today, that line lands with a potent, dispiritingly prescient thud. “The American War is over,” a character announces early in “Da 5 Bloods,” referring to the Vietnamese people’s name for the conflict. Spike Lee is here to remind us that the war for America rages on.

R. Available on Netflix. Contains strong violence, grisly images and pervasive coarse language. 154 minutes.