MOSCOW -- The nuclear meltdown at Chernobyl 20 years ago this month, even more than my launch of perestroika, was perhaps the real cause of the collapse of the Soviet Union five years later. Indeed, the Chernobyl catastrophe was an historic turning point: there was the era before the disaster, and there is the very different era that has followed.

The very morning of the explosion at the Chernobyl nuclear station on April 26, 1986, the Politburo met to discuss the situation, and then organized a government commission to deal with the consequences. The commission was to control the situation, and to ensure that serious measures were taken, particularly in regard to people's health in the disaster zone. Moreover, the Academy of Science established a group of leading scientists, who were immediately dispatched to the Chernobyl region.

The Politburo did not immediately have appropriate and complete information that would have reflected the situation after the explosion. Nevertheless, it was the general consensus of the Politburo that we should openly deliver the information upon receiving it. This would be in the spirit of the Glasnost policy that was by then already established in the Soviet Union.