In Poland, Katyn is synonymous with the oppression and terror of the Soviet occupation. In the spring of 1940, the Soviet secret police, the NKVD, murdered almost 15,000 Polish army officers and soldiers.The mass graves were discovered by German soldiers invading from the other direction. The Soviets claimed the Nazis had committed the murders. Not until 1990 did Mikhail Gorbachev admit that the Soviets bore sole responsibility. In April, for the first time ever, the heads of government of Russia and Poland will commemorate the Katyn massacre — a gesture with great symbolic value, intended to relax the tense relationship between the two countries.