following closely on the heels of the runaway success of my “most important battle” thread, what is the most significant day in the 20th century? My vote is for June 22, 1941: Operation Barbarossa. Made defeat of Hilter all but inevitable, led to the Cold War, the division of Europe, the division of Germany, unbelievable slaughter, and a host of other things. IT's ripples are still being felt now.
I would agree with johnnyjmboy, and I was going to mention that beforehand. The dropping of the first atomic bomb really signaled an end not only to old war tactics, but also the beginning of a new geo-political framework. Although conventional weapon wars still cover the globe, we have not seen wars on the scale of a continental one since WWII. This is quite impressive, given the nature of conflicts that plagued Europe through the 19th Century and in centuries earlier. Today, the ultimate political concern of world superpowers is the proliferation and use of nuclear weapons. This will not change until some nation actually attacks another with such weapons, at which point we'll have problems of global proportions - a possible "Extinction Level Event".
On June On June 28, 1914, at approximately 11:00 am, Franz Ferdinand and his wife were killed in Sarajevo by Gavrilo Princip, a member of Young Bosnia (or perhaps The Black Hand). The event, known as the Assassination in Sarajevo, was the trigger of World War I. Franz Ferdinand is interred in Schlo? Artstetten, Austria.Nothing has been the same since.
Stumpfoot, excellent answer. That day certainly must rank highly. It began a series of events which established a new era in Europe and the world. It was only really because of World War I that we had World War II; it was only in the aftermath of World War II that we entered the Cold War; and with the Cold War some modern-day Islamic militants are able to battle us in modern times.