Looking back through history, there are multiple instances of what could be considered once-in-a-lifetime occurrences. At the time, World War One was thought to be the war to end all wars, yet that wasn't the case; however, it ushered in modern ethics and views of how wars are fought.
It began with the Assassination of ArchDuke Ferdinand, which set off a chain of events that saw a large portion of the world fighting. Then, there was the fall of the Russian Monarchy, and with the deaths of the Last Czars, a new regime took over in its place, thus forming the Soviet Union, which would remain in power throughout the Second World War and until its collapse in 1991.
Going back even further, the fall of the Roman Empire was the catalyst for the forming of the Middle East and other Eastern countries, yet in the end, not much truly changed.
