It appears (not for the first time) that they have found WMD in Iraq.

"American commanders said today that they had discovered an Iraqi artillery shell last week containing sarin, one of the deadly nerve agents that Saddam Hussein said he had destroyed before the war began last year.

The shell, which had been fashioned into a bomb, was discovered as an American convoy made its way through Baghdad on Saturday, the American military officials said. Two American weapons experts suffered minor exposure to the nerve agent when they tried to defuse the shell, but they were not seriously harmed, the officials said.

[snip]

American military commanders said that the people who had planted the shell apparently believed that it was an ordinary shell filled with high-explosives, and that they had set it to explode like the dozens of others that have bedeviled American soldiers here."

[snip]

An artillery round of the type found on Saturday holds the ingredients for making sarin in two separate chambers. When fired by an artillery piece, the chambers rupture as the shell spins in flight, their contents mingling to produce sarin.

General Kimmitt said it was extremely unlikely that such mixing could occur by simply blowing up the shell, as occurred on Saturday. "

If I understand correctly, not all Iraqi nerve gas shells were binary, so the next time, if there is a next time, could be much worse. Since it appears that the insurgents didn't know that the unmarked shell was a chemical munition, it seems to me very possible that it is still around because the Iraqi armed forces lost track of it. That is, the new evidence is consistent with the current hypothesis that they attempted to destroy all of their undiscovered WMD in 1992.
If so, one can hope that there are few misplaced chemical shells.

Of course it is also possible that there are many chemical shells which were deliberately kept disguised as explosive shells.

The most alarming possibility is that the insurgents were attemtpting to release Sarin and that they will figure out how to mix the contents of the two chambers without artillery. I have no idea of how difficult that would be.

In my first post on Iraq, I wrote that the strongest case against invading was based on the likelihood that WMD would end up in the hands of terrorists if and only if the US invaded Iraq for a while. I still consider the risk that there are many such nerve gas shells disguised as explosives to be a very strong argument against the invasion. Much more recently I wrote that the absense of WMD in Iraq was one reason that I was less sure than I had been that the invasion was a mistake. My unsureness has been shaken by the news.