Why did so many Lebanese civilians lost their lives to Israeli bombing? The government line is that the IDF was doing the best it could, but these deaths were the result of Hizbullah hiding its rockets and fighters among civilians. But that assertion doesn't stand up to the facts. Of course Hizbullah did sometimes hide among civilians, breaching its duty to do everything feasible to protect civilians and possibly committing the war crime of deliberate shielding, but that's not the full story. Human Rights Watch investigated some two dozen bombing incidents in Lebanon involving a third of the civilians who by then had been killed. In none of those cases was Hizbullah anywhere around at the time of the attack. How do we know? Through the same techniques we use in war zones around the world to cut through people's incentive to lie. We probed and cross-checked multiple eyewitnesses, many of whom talked openly of Hizbullah's presence elsewhere but were adamant that Hizbullah was not at the scene of the attack. We examined bombing sites for evidence of military activity such as trenches, destroyed rocket launchers and military equipment, or dead or wounded fighters. If we were unsure, we gave the IDF the benefit of the doubt. The case of Kana shows how this works. After two Israeli missiles killed 28 civilians in a house there on July 30, the IDF initially charged that Hizbullah had been firing rockets from the vicinity of the targeted house. But Human Rights Watch investigators who visited Kana found that there had been no Hizbullah presence near the bomb site at the time of the attack. IDF sources later admitted to an Israeli military correspondent that Hizbullah wasn't shooting at all from Kana that day. In some cases, the IDF trotted out video of Hizbullah firing rockets from a village. But it has yet to show that Hizbullah was in a civilian building or vehicle at the time of an Israeli attack that killed civilians. Blaming Hizbullah is simply not an honest explanation for why so many Lebanese civilians died. And without honest introspection, the IDF can't meet its duty and self-professed goal to do everything possible to spare civilians. HIZBULLAH CERTAINLY should not be let off the hook. Human Rights Watch has conducted detailed investigations of the militia's obvious war crimes - its deliberate efforts to kill Israeli civilians by indiscriminately targeting Israeli cities. Israel had every right to try to stop Hizbullah from raining death and destruction on its people. But under international humanitarian law, just as Israeli abuses in Lebanon did not justify reprisals against Israeli civilians, so Hizbullah's war crimes did not justify Israel shirking its duty to protect Lebanese civilians. So what was the cause of so many civilian deaths? The IDF seemed to assume that, because it gave warnings to civilians to evacuate southern Lebanon, anyone who remained was a Hizbullah fighter. When the IDF saw a civilian home or vehicle that Hizbullah might use, it often bombed, even if, as in Kana, Srifa, Marwahin, or Aitaroun, there was no evidence that Hizbullah was in fact using the structure or vehicle at the time of attack. In weighing the military advantage of an attack against the civilian cost, the IDF seemed to assume no civilian cost, because all the "innocent" civilians had supposedly fled. Through these calculations, the IDF effectively turned southern Lebanon into a free-fire zone. But giving warning, as required by international humanitarian law, does not relieve the attacker of the duty to distinguish between civilians and combatants and to target only combatants. Otherwise, Palestinian militants might "warn" Israeli settlers to leave their West Bank settlements and then be justified in attacking anyone who remained. Hizbullah might have done the same in northern Israel. Nor does an evacuation warning mean that all civilians did in fact flee. Many remained in southern Lebanon because of age, infirmity, inability to afford exorbitant taxi fares charged for evacuation, or fear of becoming yet another roadside casualty of IDF bombing. As a result, the IDF's indiscriminate bombardment had devastating consequences for civilians. SO HOW SHOULD the IDF fight such a war? By complying with international humanitarian law. That means not treating southern Lebanon as a free-fire zone. It means attacking civilian structures and vehicles only if there is evidence that Hizbullah is actually using them. Even then, it means making serious efforts to determine whether civilian structures and vehicles contain civilians, and attacking only if the definite military advantage is so powerful that it justifies their deaths. Above all, it means treating Lebanese civilians as human beings whose lives are as valuable as Israelis'. Protecting Israelis from Hizbullah's deadly rockets is vital, but it does not justify indifference to the taking of civilian lives on the other side of the border. The writer is Executive Director of Human Rights Watch in New York.