Yet his interest in a global conflict that was finished before he was even born bears all the hallmarks of an obsession. By contrast, Robert Altman, a fellow director who was a participant in the war, is, judging by his work at least, far less concerned. What is it that draws Spielberg to the Second World War again and again?
It goes far beyond an interest in the Holocaust. Spielberg made his first Second World War movie aged just 12, and since then he has made four feature films explicitly about the war and several others with a Second World War context (the Indiana Jones series), and others which have updated Second World War stories (Always), featured ghosts from the conflict (Close Encounters of the Third Kind), or have characters scarred by their wartime experience (Quinn in Jaws, whose hatred of great white sharks is caused by a wartime experience), or have segments about the war (Amazing Stories: The Movie).
Self-evidently, the war occupies a special place in Spielberg's consciousness, a fixation which is slightly baffling in a Vietnam-draft generation kid. One explanation may be his idolisation of David Lean. After all, he cited Lean's Bridge on the River Kwai (1953) as the film that has most influenced him. As a child, Spielberg was particularly fond of acting out to his classmates the scene in which the wounded Alec Guinness falls on a dynamite plunger - a scene partially re-created in Saving Private Ryan.
There was also plenty at home to foster the young Spielberg's fascination with the war. Arnold Spielberg, the director's father, had been a radio operator with a B52 bomber squadron which destroyed Japanese railroads in Burma (among whose targets would have been a certain bridge on the River Kwai). "My father filled my head with war stories," Spielberg once said. "I have identified with that period of innocence and tremendous jeopardy all my life. It was the end of an era, the end of innocence, and I have been clinging to it for most of my adult life."
There was nothing innocent about his childhood love of blood and guts. As a child growing up in New Jersey, his interest in mock Second World War battles went far beyond the martial fantasies of the average little boy. He would stage four-day toy soldier battles in the basement. It was a serious business. A childhood friend, talking to Spielberg's biographer, Joseph McBride, recalled that Spielberg "always played with a box of nails and a hammer. When the soldiers were hit... he'd put nails into them, and use ketchup for blood."
The extraordinarily gory battle scenes of Saving Private Ryan are not as uncharacteristic of the director of ET as might be supposed. Spielberg is a closet gun nut, something which he likes to keep quiet about, according to the actor Charlton Heston in his autobiography, In the Arena. Heston describes Spielberg's personal arsenal of weapons as "one of the finest" in California.
From his earliest days, Spielberg also enjoyed alarming his mother by smearing himself with mulberry juice and rushing indoors to brandish his bleeding "wounds" at her. Blood and death appear to have been inextricably linked in his mind. In his first effective short film, Fighter Squadron, begun when he was 12 years old, Spielberg performed a cameo as a German fighter pilot slumped forwards in the cockpit, with black food-dye drooling from his mouth in imitation of blood.
In the same year he also made the 40-minute Escape to Nowhere (which has remarkable plot resemblances to Saving Private Ryan), a film notable for its liberal use of tomato ketchup. The gory special effects earned Spielberg an amateur film prize and obviously instilled in the nascent director the importance of effective gore. He never looked back. "My special effects were great," Spielberg proudly recalled later.
His early flair for these effects was honed by much of the Second World War paraphernalia which was lying round the Spielberg family home. In one incident, he put his father's flying cap and goggles on to a plastic skull, placed a light bulb inside it and locked his sisters in a cupboard with it. One of the sisters, Anne, went on to write the Tom Hanks vehicle Big - about a boy who suddenly finds himself in a man's body - widely supposed to be a comment on her brother.
But Spielberg has not always been successful in pursuing his war fixation: the 1979 turkey 1941, which John Wayne tried to talk him out of directing, was a misjudged comedy about a Japanese attack on Los Angeles. Many of the war movies he hoped to make never got made. In 1969, soon after his first modest successes, he tried to develop a Second World War "dogfight film" with Carl Gottlieb (who eventually wrote the shooting script for Jaws). Second World War themes continued to gnaw way at him (though in 1973 he turned down directing MacArthur because "he was wary of the logistical problems of staging the Second World War"). He was both attracted to and over-awed by the subject. In Close Encounters, he changed the main protagonist from an airman to a civilian because "I find it very hard to identify with anyone in uniform".
And yet, with his latest film, Saving Private Ryan, he has confounded his own reservations by managing to create convincing military characters who struggle with their masculinity in classic Spielbergian dilemmas (an all-male cast seems to suit him). Though topped and tailed with scenes of cloying sentimentality, the majority of the film ranks amongst the finest work Spielberg has ever done. Once again he has underscored his primal, childish impulses - in this case, a squeamish love-hate of gore - with a range of extraordinary adult emotional themes.
There are more war clouds on the horizon: Spielberg is currently in pre- production with another Second World War-era movie, this one based on Arthur Golden's best-selling novel, Memoirs of a Geisha.
Will Hollywood's wunderkind ever get to the bottom of his obsession? With Saving Private Ryan, Spielberg can at least feel that he has answered John Wayne.
"I'm surprised at you," growled the Duke, after reading the script for 1941. "I thought you were an American, and I thought you were going to make a movie to honour the memory of the Second World War."
Twenty years on, Spielberg has done exactly what John Wayne wanted him to do. He has honoured his parents' generation, and perhaps purged some of his own personal demons along the way.