This much about the gassing at Halabja we undoubtedly know: it came about in the course of a battle between Iraqis and Iranians. Iraq used chemical weapons to try to kill Iranians who had seized the town, which is in northern Iraq not far from the Iranian border. The Kurdish civilians who died had the misfortune to be caught up in that exchange. But they were not Iraq's main target.

And the story gets murkier: immediately after the battle the United States Defense Intelligence Agency investigated and produced a classified report, which it circulated within the intelligence community on a need-to-know basis. That study asserted that it was Iranian gas that killed the Kurds, not Iraqi gas.

The agency did find that each side used gas against the other in the battle around Halabja. The condition of the dead Kurds' bodies, however, indicated they had been killed with a blood agent -- that is, a cyanide-based gas -- which Iran was known to use. The Iraqis, who are thought to have used mustard gas in the battle, are not known to have possessed blood agents at the time.

These facts have long been in the public domain but, extraordinarily, as often as the Halabja affair is cited, they are rarely mentioned. A much-discussed article in The New Yorker last March did not make reference to the Defense Intelligence Agency report or consider that Iranian gas might have killed the Kurds. On the rare occasions the report is brought up, there is usually speculation, with no proof, that it was skewed out of American political favoritism toward Iraq in its war against Iran.

I am not trying to rehabilitate the character of Saddam Hussein. He has much to answer for in the area of human rights abuses. But accusing him of gassing his own people at Halabja as an act of genocide is not correct, because as far as the information we have goes, all of the cases where gas was used involved battles. These were tragedies of war. There may be justifications for invading Iraq, but Halabja is not one of them.