The spring of 1942 was a perilous time for Americans, caught, as they were, in a new war. The preceding December, the Japanese had bombed Pearl Harbor. American troops in the Philippines were close to surrender. The Wehrmacht had advanced across Europe and into the Soviet Union and North Africa. Many people wondered whether the United States had a “crusading faith” to fight for. In April, Frank Capra, the ebullient director of “It Happened One Night” and “Mr. Smith Goes to Washington,” stepped into the Museum of Modern Art to see, for the first time, Leni Riefenstahl’s “Triumph of the Will,” a celebration of the Nazis’ 1934 Party congress, in Nuremberg. Again and again, Riefenstahl makes heraldic use of torchlight parades, banners, and trumpets raised to the sky like artillery. German history, German labor, and German military force are summoned to communal ecstasy, as Adolf Hitler, in a guttural roar, demands obedience and victory. The movie was overwhelming, mystical—a product of romanticism and modernism pushed to extremes. Capra was shocked. In later years, he often told the story of seeing the film. One of his initial reactions was “We’re dead. We’re gone. We can’t win this war.”

“Triumph of the Will” was a call to hatred and to combat, but Capra had additional reasons to be alarmed. Eager to serve, he had enlisted in the Army shortly after Pearl Harbor, and had agreed to make training films for recruits. George C. Marshall, the Army Chief of Staff, was assembling a vast fighting force, and many of the young draftees and volunteers were isolationist, ignorant, or indifferent. Marshall wanted to explain to them the aims of the war and the nature of the enemy; he wanted soldiers who knew what they were fighting for. The Army had commissioned a series of lectures on military history from the end of the First World War through 1939, but lectures put recruits to sleep. And Marshall was not impressed by what the Army’s Signal Corps—which had used films for training purposes since 1929—was turning out. Capra knew that he had to find an explicitly American way of selling the war to soldiers and to the public as well; he became one of the key figures in the largest movie-propaganda campaign the government had ever undertaken.

A number of Hollywood directors signed up, and, as Mark Harris writes in “Five Came Back: A Story of Hollywood and the Second World War” (Penguin), the most prominent among them had different ambitions and needs. Capra, a Sicilian immigrant who had found success in the United States, was an emotional patriot; his films expressed a boyishly guileless belief in American goodness. The truculent, sometimes alcoholic, but indefatigable John Ford, who between 1939 and 1941 had made seven major movies (“Stagecoach,” “Young Mr. Lincoln,” “Drums Along the Mohawk,” “The Grapes of Wrath,” “The Long Voyage Home,” “Tobacco Road,” and “How Green Was My Valley”), loved the military, especially the Navy; he wanted to go to the front and record what the fighting man was experiencing. William Wyler was a legendary perfectionist, who directed such Bette Davis classics as “Jezebel” and “The Letter.” When Pearl Harbor was attacked, he was working on “Mrs. Miniver,” a celebration of middle-class Britons in wartime, and he deliberately turned the film into sentimental propaganda. It became a huge hit and won six Academy Awards, but Wyler began to feel that “Mrs. Miniver” was naïve. Filming combat in the European Theatre became for him an emotionally indispensable “escape into reality.”

John Huston, who began as a screenwriter, and, in 1941, directed “The Maltese Falcon,” was a roughneck of literary bent who longed for danger and excitement. He, too, wanted to put something more demanding on the screen than Hollywood’s genteel standards allowed. George Stevens, the creator of the classic Astaire-Rogers musical “Swing Time” and the Anglophile adventure “Gunga Din,” had actually tried to adapt Humphrey Cobb’s bitter First World War novel “Paths of Glory” but was unable to persuade his studio, RKO, to take it on. (The book was eventually filmed, in 1957, by Stanley Kubrick.) Instead, Stevens made comedies like “Woman of the Year” (the first Tracy-Hepburn film) and “The More the Merrier,” and, by 1943, he had begun to think of his films as trivial. They weren’t, but he also desperately needed to get out of Hollywood.

These five men were at the heart of the establishment, but they rebelled against it. Even Capra was dissatisfied—“bored,” he later said, with what he was doing. The studios, having largely ignored Nazism throughout the nineteen-thirties, made countless combat films in 1942 and 1943, and inserted war boosterism into romances, musicals, and gangster movies. (Sherlock Holmes and the Invisible Man were updated and turned into Nazi hunters.) These five men wanted none of that. They gave up honeyed lives and big Hollywood projects and submitted, at military pay, to the frequent interference of bureaucrats in the War Department in order to make films that they thought the country needed—and that they needed themselves.

Fusing art, politics, and history, Riefenstahl had composed a symphonic ode to domination. For the American filmmakers, living in a rowdy democracy, no such grand synthesis was possible, or even imaginable. But how do you create war propaganda in a democratic country? Do you just make movies promoting victory? Is it possible to work, under military sponsorship, as an artist and a truthteller?

Mark Harris’s account of the cultural and commercial shifts in the Hollywood of the late nineteen-sixties, “Pictures at a Revolution” (2008), is a film-history classic. He’s a good storyteller and a good critic: he describes both documentaries and features with warmth and perceptive detail. “Five Came Back” is a splendidly written narrative, but it presented Harris with a structural problem. Moving slowly and steadily, he uses the directors’ adventures as a way of informally telling the story of America’s participation in the war. It’s a strategy that causes him to jump back and forth among his heroes, and, at times, he leaves a director stranded at the start of a project, crew at the ready, only to pick him up thirty pages later. Writing a definitive history has its perils, and Harris tells us more than we want to know, chronicling aborted or stalled projects and endless tussles with the military over assignments and the tone and the explicitness of combat footage that the public might see. But his characterization of the directors is shrewd and engrossing, and he’s at his best when he dramatizes the men facing live fire and grappling with the film medium.

On occasion, Capra assigned documentary projects to Huston or Wyler, but most of the time he devoted himself to fulfilling Marshall’s request to indoctrinate recruits. He outlined a seven-part series of films called “Why We Fight,” and, in the first film, “Prelude to War,” he laid eager hands on Axis propaganda, including “Triumph of the Will.” Capra repurposed (i.e., stole) some of Riefenstahl’s most remarkable images (the camera descending slowly, as if from heaven, into a vast stadium filled with men). “Let our boys hear the Nazis and the Japs shout their own claims of master-race crud,” Capra said, “and our fighting men will know why they’re in uniform.” “Prelude to War” traces the rise of the Nazi Party and of the militarist élite in Japan. It ends with the two nations prepared to engulf their neighbors.