The Katyn Massacre

KATYN, RUSSIA - MARCH 1942: (POLAND AND RUSSIA OUT) Polish compulsory workers put crosses when they knew about the massacre. The Katyn Massacre of 1940 was w mass execution of Polish military officers by the Soviet Union during World War II. The discovery of the massacre precipitated the severance of diplomatic relations between the Soviet Union and the Polish government-in-exile in London. On April 7, 2010, Russian Prime Minister Vladimir Putin joined Polish Prime Minister Donald Tusk at a ceremony commemorating the massacre, marking the first time that a Russian leader had taken part in such a commemoration. Three days later, on April 10, a plane carrying Polish Pres. Lech Kaczynski to another commemoration ceremony crashed near Smolensk killing Kaczynski, his wife Maria and other 94 political, military and religious officials. march, 1942 (Photo by Wojtek Laski/Getty Images)