As I understand it, that movie was never released because it made General Mark Clark look like an incompentent buffoon. Clark ordered attack after attack against the German (Gustav) line, in the face of murderous fire. Terrible casualties were incurred, many from some Texas-only infantry units. Commanders of those units curse Clark's name to this day.
He said that Clark could never go to Texas, he would have been hanged to the nearest tree.
Close, except it wasn't Cassino but another hill town, San Pietro. Here's more on Huston's wartime films:
"By 1943," Mackenzie wrote in the New York Times in 2000, "when Huston went to Italy for 'The Battle of San Pietro,' he had stopped identifying with the home front and started identifying with the men he was filming."Huston's movie told of a Texas infantry regiment's attempt to liberate the hill town of San Pietro from a well-bunkered enemy who exacted a terrible toll of American casualties. Huston screened the movie for U.S. Army brass and recalled: "I remember the ranking officer rising around a third of the way through and leaving the theater. And when he was gone, the next-ranking officer rose and he left. And so they went, one after the other, until I was alone in the room."
"San Pietro" was briefly suppressed by the Army, until Gen. George C. Marshall saw it and decided it would benefit soldiers going into combat to have a realistic idea of what was in store for them.
Huston's third and last war documentary, "Let There Be Light," was actually shot after the war was over, in a military hospital on Long Island. His assignment, Mackenzie said, "was to create a sympathetic documentary on the military's rehabilitation of the 'psychoneurotic soldier,' to educate civilians and help ease the soldiers' re-entry into society."
But so devastating was the portrayal of the "casualties of the spirit," as Huston described them, that when the director attempted to screen it at the Museum of Modern Art in 1946, it was seized by military police and kept under wraps until 1980, when at the insistence of Vice President Walter Mondale it was finally declassified.