This first in John Ford's "Cavalry Trilogy"-She Wore a Yellow Ribbon and Rio Grande follow-is the most double-edged about heroism, honor and historical legend. Henry Fonda plays the martinet commandant, a Boston scholar of military history, resentful of his post-Civil War reduction in rank and obsessed with new chances for "glory" against the Indians. This is a great performance, in a surprisingly disagreeable role. Increasingly at odds with him is John Wayne as a seasoned non-com officer who is no stranger to the Apaches. Ford's vision of the Seventh Cavalry-whose job was to harry already decimated tribes-is unquestionably rosy, an ideal of community life. And it is true that the romantic subplot, with teenaged Shirley Temple as the commandant's daughter, now requires some teeth gritting. But for those who anticipate that a John Ford/John Wayne film from the forties must be mindlessly racist, Fort Apache will prove a revelation, its complexity due in part to tensions between the manifest destiny of James Warner Bellah's stories and the Eastern scepticism in the first script by Frank Nugent, longtime film critic (1934-40) for The New York Times. It is a tricky, thoughtful action picture, with a morally shocking ending, matched among Ford's Westerns only by The Searchers, My Darling Clementine and The Man Who Shot Liberty Valance (and screened tonight in a rarely seen 35mm print which shows off Monument Valley at its most beautiful). Scott Simmon