The Iraq war reminded coalition forces of a growing problem; how do you know when an electronic target you've just bombed is really damaged enough to be out of action. When you are dealing with obvious things, like radar or satellite dishes, or radio transmission towers, you are pretty certain that if the structure is blown down (or up), then transmission has ceased. But it is less certain if you are bombing an electronic switching center or a large computer facility. This is made more difficult still because the most vital parts of these installations are often underground. Thus far, the solution has been use a lot of large bombs and just smash the structure as much as possible and hope for the best. But experiments are being conducted with electronic sensors that can detect how much useful work is still going on in such targets after they are hit with fewer, and smaller, bombs. The trend is to equip American bombers with a larger quantity of smaller, and more accurate smart bombs. If the more sensitive sensors work, telecommunications and computer centers can be knocked out with fewer bombs, and less damage overall. The exact nature of how the new sensors work has not been openly discussed, no doubt because one could more easily deceive the sensors if you knew what they were looking for.