Counterfactual history, part 2 ... World War I.

A century later, NPR has been considering the "what ifs" about the Great War.

What If World War I Had Never Happened?

This summer marks 100 years since the start of World War I. Many argue that the conflict was inevitable — but what if it wasn't?

World War I was when the old world became the new. Here, a German cavalryman wears a gas mask and carries a long spear or pole, from two different ages of war.

Without the assassination of Archduke Franz Ferdinand, there would have been no need for rulers in Vienna to threaten Serbia, no need for Russia to come to Serbia's defense, no need for Germany to come to Austria's defense — and no call for France and Britain to honor their treaties with Russia.

What would be the ripples of this counter-history?