UNDER SIEGE by Elizabeth Mace. 1990, Orchard Books. 214 pages, $13.95.

It has been a long time since I thought about my friends, Lori and Ron, and their home in Ohio. Ron is a historian and his study was completely devoted to war games, battles with technical descriptions using miniature game pieces and maps to solve the conquests. The walls were spread with game plans, display cases held the models of hand-painted figures of real and make-believe combats. It was while reading "Under Siege" that the impressions of Ron's simulated battles and the tactical practice came back to me.Sixteen-year-old Morris visits Uncle Patrick in the country and finds a room filled with a model of a medieval castle, resplendent with figures that moved with the help of a computer program. "They were a load of cleverly computerized game pieces whose `minds' were factory cloned to work together, activated by some distantly pre-set program to follow an invented race myth . . . "

Morris becomes obsessed with the figures and finds that some of them can communicate with him: "He lifted the female figure out of the box and placed it on the floor; just outside the edge of her home ground, facing him . . . `I'm calling you Vail from now on.' She looked at him briefly . . . `Your hands are mine,' she said. `I will follow to the end.' "

As the peasants are threatened with battle and death through a Horse-of-Troy-like chariot, Morris fears for their lives. He studies the handbook which accompanies the miniature set and discovers the intricacies. He learns to turn the monitors to the vacant castle walls and roam, through computer pictures, into the homes and gardens of the people.

When Uncle Patrick tires of the combat and leaves it, the landscape continues to change without human hand or directives from the control panel.

Young readers will question whether the maneuvers are man-made or spontaneous in "Under Siege" but will delight in the configuration of the possibilities of the armed struggle and counter attacks that could happen with computers.

Mace has written a detailed battle story set in an English countryside. The language and British dialect flow evenly and the slang should not disturb a reader who seeks the enjoyment of the venture. The subthemes of Morris' family problems and his infatuation with the miniature figure, Vail, adds to the plot line.

While the story of the miniature castle or Morris' life is never completely resolved, it leaves room for the reader to make decisions about what might happen just as the peasants asked, "What can it mean? What shall we do? Where shall we hide?"