WWII saga of remarkable power; A Midnight Clear, by William Wharton. New York: Alfred A. Knopf. 242 pp. $12.95 .
The soldiers in William Wharton's new novel are so wholesome they almost seem more like characters from ''Leave It to Beaver'' than GIs serving on the German front in December 1944.
''Father'' Murphy frowns on profanity and works to elevate the squad's moral tone; ''Mother'' Wilkins concerns himself mostly with ''playing house,'' cleaning up after the inevitable wreckage of war; the rest of the squad, all teen-agers, are more interested in playing bridge than going on patrol.
Even the narrator, 19-year-old Sgt. Will Knott (inevitably nicknamed ''Won't''), just wants to read Hemingway and sketch the landscape. He considers the unit ''not actually part of this army. We're princely orphans left on the wrong doorstep, maybe bastards of the blood.''
The reader's sense of isolation from the real world is heightened by the novel's unusual setting, which seems drawn in equal parts from the Brothers Grimm and grim reality. Staked out in an abandoned chateau in the middle of the snow-dusted Ardennes Forest, the men are detached from all sense of time and only sporadically in touch with either side of the fighting.
Knott's unit is charged with performing intelligence and reconnaissance missions on possible German troops nearby, but as the sergeant is well aware, his squad has ''a lot of intelligence but not much reconnaissance'' as it goes through the motions of military maneuvers.
All six men are emotionally drained, the burned-out remains of a disastrous assignment in the Saar that cut their original team in half. The irony is that on their new mission they find German soldiers in the area far more affable than their own American commanders. The men slowly realize that the local Germans are somehow unwilling to attack; in one of the novel's best scenes, a skirmish with the enemy turns into a mad snowball fight.
If this fairy-tale scenario seems slightly unreal in a World War II novel, the incongruity is purely intentional. Wharton reveals the ugliness of war far better by reminding us of the joy of life than by pedantically documenting the brutality of battle.
Like the title character of Wharton's acclaimed first novel, ''Birdy,'' Sergeant Knott reacts to the confining pressure of combat by searching for uplifting mental escapes. ''I'm having my usual trouble,'' he remarks at one point, ''noticing how beautiful the world is just when there's a chance I might be leaving it.''
Such cynical wisecracks serve to turn potentially maudlin situations like the men's Christmas celebration into events of beguiling intensity. Knott's matter-of-fact narration and offhand conversational style turn a quirky fantasy into a drama of convincing reality. As the fairy-tale falls apart and the novel is pulled toward its explosive conclusion, we come to realize that we have been emotionally blitzed by a novelist of remarkable power.
If Knott's reflections and reminiscences are jumbled under pressure, Wharton's tight control of the novel is not. Besides, as one of the soldiers in ''A Midnight Clear'' points out, ''None of it makes sense. How do you make sense inside something like war which is basically nonsensical?''