America's most-advanced tank, the M1A1 Abrams was disabled by some sort of RPG. I say "some sort of RPG" because officials aren't sure exactly what it was that hit the tank on patrol in Iraq.

One armor expert at Fort Knox, Ky., suggested the tank may have been hit by an updated RPG. About 15 years ago, Russian scientists created tandem-warhead anti-tank-grenades designed to defeat reactive armor. The new round, a PG-7VR, can be fired from an RPG-7V launcher and might have left the unusual signature on the tank.

In addition, the Russians have developed an improved weapon, the RPG-22. These and perhaps even newer variants have been used against American forces in Afghanistan. It is believed U.S. troops seized some that have been returned to the United States for testing, but scant details about their effects and “fingerprints” are available.

Still another possibility is a retrofitted warhead for the RPG system being developed by a Swiss manufacturer.

At this time, it appears most likely that an RPG-22 or some other improved variant of the Russian-designed weapon damaged the M1 tank, sources concluded. The damage certainly was caused by some sort of shaped-charge or hollow-charge warhead, and the cohesive nature of the destructive jet suggests a more effective weapon than a fragmented-jet RPG-7.

The issue then becomes this: Was Russia selling these things to Iraq, in violation of U.N. sanctions? Or do the Russians have such poor controls on their advanced weapons that they allowed some to make it onto the black market and into the hands of terrorists?