World War II was a seven-year conflict that killed tens of millions, and it truly was a global war. From North Africa and the Middle East, where Axis and Allied forces fought to secure oil supplies to keep their armies and countries moving, to the Pacific, where Japan and America wrestled back and forth over one island at a time, to North America, where there was no actual fighting but a great mass mobilization reaching throughout all of society, the war to end all wars left its mark. Only South America was left mostly un-meddled with.
The most affected region, though, was certainly Europe. The Western Front reached through France and Belgium, all the way down to Italy where the fascists were pushing northward. The Eastern Front was where Nazi Germany faced off with communist Russia - the latter being an ally so vile that Winston Churchill compared being forced to team up with them to being expected to work with the Devil to stop Hitler. In between, death camps and concentration camps obliterated civilian populations with military precision. The German regime sent the Luftwaffe to bomb British towns, primarily London, and wiped Coventry off the map. In return, the British crushed Dresden. It was a bloodbath that left the continent in ruins - and all of it was documented thoroughly and is now taught in schools.
Let's see how much of this important history you've retained.