1. The Molotov-Ribbentrop Pact (1939)
Few agreements stunned the world like the Molotov-Ribbentrop Pact, a non-aggression treaty between Nazi Germany and the Soviet Union. Signed on the eve of World War II, this astonishing alliance allowed two sworn ideological enemies to carve up Eastern Europe in secret protocols. The pact set the stage for the invasion of Poland and triggered a chain reaction across the continent. Its audacity would be matched only by the later Cold War realignments that saw old enemies become uneasy partners once again.
