Most U.S. Army training bases were originally built in rural areas, and had few civilians living nearby, or within earshot of the training areas where the noise from vehicles, and weapons firing, would keep people up at night. But over the years, more and more civilians have built homes close to the base boundaries. There they discovered, too late, that the army likes to train at night, and make a lot of noise while they are doing it. People complained, causing political problems, and headaches for commanders at the bases, as they dealt with a growing number of, often quite strident, complaints. Night training has become more common over the last two decades, as night-vision equipment got cheaper, and more common. So the Department of Defense is testing a new program to buy homes within five kilometers of base boundaries, believing that a few million dollars spent now, will save far more in the future.