david_ariagno_world_war_2No conflict in human history can come remotely close to matching the devastation of the Second World War. By the time the final treaties were signed, WWII had claimed the lives of between 50 to 85 million people–soldiers and civilians alike–around the world. It left a mark on every level of society, from politics, art, diplomacy, economics, ethics, and especially the art of war itself. Even  today, its aftershocks still send the world reeling.

Contrary to popular belief, the war did not begin with the bombing of Pearl Harbor in 1941: by that point, the war had already been raging for over two years. Take a look at some of the most significant dates from WWII.

September 1, 1939

In what is widely considered to be the first day of the war, Germany invaded Poland in a strategy that came to be known as a blitzkrieg, or lightning war: a surge of coordinated air raids followed by tank assaults. Germany was able to take control of Poland with little resistance. However, on Sept. 3, England and France declared war on Germany when it refused to withdraw forces from Poland, thus officially opening WWII.

December 7, 1941

President Franklin Delano Roosevelt declared Dec. 7 to be “a date which will live in infamy” after the Japanese attack on Pearl Harbor. The surprise attack came as America was in the midst of peace negotiations with Japan, so the bombings caught the U.S. Navy completely off guard; by the time the smoke cleared, Japanese warplanes managed to sink four American warships and kill more than 2,000 servicemen. The attack on Pearl Harbor was launched simultaneously with attacks on U.S. positions in the Philippines and other nearby islands, and while its goal was to cripple America’s Pacific fleet, Japan’s strike on Pearl Harbor inspired America to finally enter the war.

June 6, 1944

The largest amphibious assault in history, the Allied invasion of Normandy–popularly known as D-Day–witnessed the landing of more than 24,000 Allied troops on several beaches in northern France, which was then under Nazi control. Despite inclement weather, the Allies were able to storm the coast and drive back German defenders, paving the way for the liberation of France and the defeat of the Nazis.

August 6, 1945

Three months after Hitler’s death and the surrender of the Nazis, the United States dropped the first atomic bomb–codenamed “Little Boy”–on the Japanese city of Hiroshima. Between 70,000 and 80,000 were killed by the blast and the firestorm that resulted from it, and when Japan did not immediately surrender, President Harry S. Truman threatened to unleash a “rain of ruin” against Japan and ordered another atomic bombing on the city of Nagasaki on Aug. 9. Japan surrendered unconditionally to the Allies on Aug. 15 after being brought to its knees by atomic bombings.