Spike Lee sometimes makes movies that are too provocative for critics to think straight. It’s hard to imagine, say, his complex 2000 satire on race and the press, “Bamboozled,” enjoying widespread acclaim upon its release, no matter its quality. But Mr. Lee’s new World War II film, “Miracle at St. Anna,” which opens Friday, is not an example of the director’s volatile filmic chemistry blowing up the laboratory. It’s just not very good, never mind compelling enough to sustain a 160-minute sprawl that, at the end, leaves one puzzling over where exactly the time went.

Adapted from the novel by James McBride, “Miracle at St. Anna” is about four American soldiers from the all-black 92nd Division who become marooned in an Italian mountain village behind enemy lines. They’re survivors of a riverside slaughter partly caused by a racist commander’s intransigence. A cast of young actors (Derek Luke, Michael Ealy, Laz Alonso) play three of the “Buffalo Soldiers,” with Omar Benson Miller in the fourth, irredeemable role of a superstitious Southern simpleton. A fearful Italian family’s house provides shelter within the labyrinth of stone walkways and houses.

Bookending “Miracle” is a mystery, set in 1983, about a black postal worker who shoots a customer for no apparent reason. This strange frame is, typically enough, one of Mr. Lee’s better moves, a blunt but interesting displacement of war’s unknowability to outsiders. But the wartime subplots, in the screenplay by Mr. McBride, are poorly juggled and conceived; the friendship between Mr. Miller’s character and a traumatized, possibly insane Italian boy, is a maudlin mess, as are the divisions within a local group of Italian partisans. A fierce street battle at the end is at least often nerve-wracking, and Mr. Lee’s frequent director of photography, Matthew Libatique, achieves a humid prestige look.

Early in the segment set in 1983, a black veteran is shown talking back to a TV broadcast of John Wayne blustering in “The Longest Day,” underlining the avowed purpose of “Miracle”: to represent the experiences of black soldiers to an extent never achieved in war cinema. But in a sense, Mr. Lee has tragically tried to remake all of those movies at once, up to and including the true horror story of the Nazis’ massacre of 560 Italian civilians. The result is exhausting for the wrong reasons, instead of being as disarming and adventurous as the filmmaker can be at his best.