In September 1939, Germany and the Soviet Union invaded and occupied the republic of Poland, dividing the country between them. Some two hundred thousand Polish soldiers became prisoners of war in Russian camps, which were often converted monasteries. In March 1940, Joseph Stalin approved a plan to murder twenty-two thousand officers, sergeants, and civilian intellectuals, the better to deprive eastern Poland of the men who might contest communist rule when the eastern half of the country was incorporated into the Soviet Union.

After the German invasion of Russia the following year, the first mass graves were uncovered and revealed to the world by Nazi propagandists. The Russians in turn blamed the atrocity on the Germans, claiming that the bodies were actually Jews dressed in Polish uniforms. Britain and the United States accepted this fabrication so as not to harm their alliance with the Soviet Union. But in 1952 the U.S. Congress convened hearings that convincingly laid the murders at the doorstep of Stalin himself. This is the story of those findings.