Only during World War I. For the last several hundred years, historically the "greatest period of change" has always been "right now."
it is obviously WAR, and CLIMATE CHANGE
World War I was the biggest war in memory for the people during that time period. I believe they called it the war to end all wars. They hadn't had World War II yet, and so they though that World War I was going to be the biggest war in history for all time.
world war 1
world war 2
the biggest war of all is world war 2 but most people say it was the civil war p
I am not being facetious: The biggest effect of World War I was World War II.
World War one was the first great war. It was the biggest war the world had seen and involved many countries.
world 2 war
It brought about the biggest change to warfare in human history, comparable only to the creation of modern warfare from the First World War.
Third period of World War II happened in 1945.
Germany
Poland.