The bombing of the Chinese Embassy in Belgrade is a sobering reminder that precision-guided munitions are explosive junk unless they are backed up by precision-guided minds.
The age of high-tech targeting may have greatly reduced inadvertent casualties, but it hasn't eliminated them. The latest incident joins a list that stretches from a bunker full of Iraqi civilians hit in the Gulf War to the two NATO missiles that have skipped into Bulgaria in recent weeks.
Whether the mistake that caused the bombing - use of outdated targeting maps - turns Western publics against NATO's war with Yugoslavia remains to be seen.
The test will be how much the public values returning Kosovar Albanian refugees to their homes. Are the stakes of the conflict worth unforeseen casualties?
"The great limiting factor of American military power is the American public," says retired Army Col. Harry Summers, a fellow at the Army War College in Carlisle, Pa. "That is the specter hanging over Clinton's head."
The US military has long relied on the promise of new guidance and communications technologies to make its means of waging war as precise as possible. The point is both to limit damage to innocent bystanders, and to make the waging of war efficient but deadly.
Bombs that ride laser beams down to their targets are only the first generation of such precision-guided munitions (PGMs). The state of the art might be a new prototype bomb whose fuse senses when it is in the correct room of its target building, and explodes accordingly.
If nothing else, the explosion of B-2 satellite-guided PGMs in a complex that houses innocent foreign diplomats shows that the new microchip technology has not reduced conflict to an antiseptic video game.
An intelligence failure caused the accident, said US officials over the weekend. CIA analysts drawing up target lists used outdated maps that did not show the Chinese Embassy at its present location. They thought the spot marked an arms procurement agency - a mistake that was not caught by US military staff.
Such human mistakes have been the cause of some of the worst instances of collateral damage inflicted by US forces in recent years. In 1988, a US cruiser mistook an Iranian airliner for a hostile warplane and shot it down over the Persian Gulf.
At the height of the Gulf War, US warplanes hit a bunker believed to sheltered Iraqi commanders. Instead, it contained hundreds of civilians who had sought safety from allied attacks.
THIS does not mean that US military technology always works as advertised. Laser-guided PGMs are prone to being diverted by winds or clouds, which can cause them to lose sight of their laser and wander off course.
Antiradar missiles, which ride a radar's electronic beam down toward their target, can skip away if the radar crew turns off their equipment fast enough. That is apparently what happened in at least two other instances of collateral damage in the Yugoslav conflict, when NATO missiles flew into neighboring Bulgaria.
NATO says that fewer than 10 of its weapons have gone off course and caused civilian damage in the current air campaign. Aside from the embassy bombing, the worst incidents have involved pilots flying too high to see that a bus was crossing the bridge they had targeted - or that the vehicles they were attacking were tractors, not tanks.
These incidents, say experts, were the direct result of one of NATO's political imperatives: Avoid pilot casualties at all costs.
"Our pilots are at 30,000 feet and there are no forward air observers on the ground," says Richard Shultz, director of International Security Studies at Tufts University's Fletcher School of Law and Diplomacy in Medford, Mass. "The reason for that is we don't want to put anyone at risk."
As this shows, the issue of collateral damage is inextricably entwined with complex political calculations. Incidents of unplanned damage have to be judged in their own context, say experts.
Thus in World War II, Allied bombing campaigns inflicted over 1 million civilian casualties in Europe. The nature of air war made it much more dangerous to civilians: In the days of B-17s, it took 9,000 unguided bombs to destroy an aircraft shelter, according to a General Accounting Office report. By the Gulf War, the same job could be done by one to four PGMs.
Of course, World War II was a long and brutal war against brutal enemies for the future of Western civilization. There was little focus on collateral damage until near the end of the war.
"When passions and stakes are high, we will both accept and inflict casualties without batting an eye," says Colonel Summers.
In Vietnam, public opinion about the bombing of the North wavered in proportion to questions about the nature and worth of the overall US effort.
In the Gulf War, there was much collateral damage, from Kuwait's oil pumps to Iraqi bunkers. But with a clear war goal in mind, Western publics were largely unmoved.
In the current conflict, "the American public ... has focused on the [Albanian] refugees," says Allen Weinstein, president of The Center for Democracy in Washington. "They have not ignored the issue of collateral damage and civilian targets, but see them in context."