6. The Nazi Invasion of Poland (1939)
On September 1, 1939, Nazi Germany launched a swift invasion of Poland, employing blitzkrieg tactics that overwhelmed Polish defenses. This assault led to the partitioning of Poland between Germany and the Soviet Union, as per the secret protocol of the Molotov-Ribbentrop Pact. The occupation resulted in the deaths of approximately six million Polish citizens, including three million Jews, and subjected the nation to decades of oppression and destruction (britannica.com).
