Not that long ago, training simulators didn't draw many gee-whizzes in the American military. Sure, they were useful tools, helpful in training aviators, tank commanders, and ship-drivers. And they had come a long way from the primitive joy-sticks hooked to cathode-ray-tube monitors that had begun to appear in the early 1980s.
But they also had serious limitations. Many still depended on using actual equipment—a real airplane or tank cockpit, or a re-creation of a ship's bridge—that was costly to put together. The computers they used were sluggish, and the software was primitive, with only middling resolution, not all that realistic. And they provided relatively few options for varying the training scenarios.