German Prisoners on the American Home Front : THE TURKEY WAR <i> by Douglas Unger (Harper & Row: $16.95; 226 pp.) </i>

All of us who creak through middle age remember the Andrews Sisters singing “Don’t Sit Under the Apple Tree. . . .” and the 3 gallons of gasoline per week allowed with an A coupon, and the shortage of able-bodied young men--whether to do the work or dance the jitterbug.

We won’t forget Rosie the Riveter, who put on slacks--and took up the slack--a pioneer feminist who was too busy to realize she may have inspired a movement.

But few of us remember that German prisoners of war also took up the slack, picking, plucking or packing at farms and factories all over the center of the United States. They were brought by ship, not so unlike the slaves, and then taken by train to labor camps.

Douglas Unger isn’t old enough to remember but he is bright enough to mine this 45-year-old anomaly of American life as fiction. “The Turkey War” is a microcosmic conflict of wills, at dirt level, in the midst of a global conflict that would end at impersonal bombing level.

Mose Johnson is a good, simple man whose wife has left him and whose farm has failed him. His job as yardman at the Nowell-Safebuy turkey processing plant has been upgraded, against his wishes, to production manager, probably for the duration.

Harmut von Ujatz is an aloof, rigid man whose Afrika Korps troops have been killed or captured and whose command has been transferred to a prison camp. His job has been downgraded to overseeing hundreds of transplanted Germans picking beets or packing turkeys in South Dakota.

These two men are both prisoners of a peculiar time and place. Johnson, the unwilling foreman, has to make the Germans process turkeys at record-setting pace for the war effort. Von Ujatz, known as the Hauptmann (Captain), has to keep his men alive, as Germans, as soldiers--and as potential escapees.

Men with P.O.W. stitched across their backs, without money and without English, can hardly escape from the middle of America but the Hauptmann can deploy his troops at the Nowell-Safebuy plant, assuring them their rights as prisoners, demanding safe operating procedures and--when it suits his purposes--slowing down or even hobbling production by reassigning the work force.

For a time, the Germans perform superbly, learning the tricks of gutting and boning birds, rebuilding themselves a prison camp complete with vegetable gardens, a movie theater showing “Andy Hardy’s Double Life” and a weekday beer hall that serves as a Sunday church. Camp Orman was almost Eden after the miseries of North Africa combat. Keller, one of the few Germans who speaks English, tells Johnson: “Hitler left us in the desert with nothing. No food. No water. No bullets. Berlin just tossed us into the trash heap to die.”

Unger flips the usual P.O.W. story upside down. The captured Germans appear as downtrodden human beings, not as monsters from the master race nor as buffoons. The U.S. soldiers who guard them appear as inept--and at times corrupt--people, the men not good enough for Europe or the Pacific. Only the Hauptmann , unwell but unbending, seems to be the prototypical Prussian. His men, by contrast, behave like factory workers anywhere, putting in their time.

Keller, the English-speaking prisoner, juggles his loyalties--an interpreter-helper for Johnson, a soldier under the Hauptmann’ s command. This man, caught in the impossible middle, eventually turns out to be the only real survivor of “The Turkey War.”

Johnson’s troubles mount as he tries to meet his quotas, attempts to quell resentments among remaining American workers and works at treating the prisoners as more than processing machines. At the same time, Johnson has a personal problem trying to stay away from Carol McCann; she’s the big-boned and sometimes brazen farm woman whose husband is fighting overseas. The more Mose’s troubles tumble upon each other, the more often he spends his evening at the only bar in town.

Author Unger has his own troubles. The humiliating end for Johnson seems inexorable and exactly right--the tragedy of a decent man sent into a conflict he never chose. World War II wrecked many lives, even thousands of miles from the battlefronts. But while the reader comes to like Johnson and comes to admire Keller, the Hauptmann remains something of a mystery. The end for Von Ujatz is more an assertion than an exploration of character.

As an unearthing of forgotten special circumstance, the novel is excellent literary archeology. As a clash of characters, the novel concentrates on only one character. Mose Johnson never fully recognizes what moves his implacable opponent; neither, alas, does the reader.