1910-1920: Largely as a result of the introduction of new weapons such as tanks, poison gas, and airplanes, more than ten million people die in World War I, creating an atmosphere of pervasive disillusionment and despair.

Today: Technological advances make it easier for countries and individuals to develop nuclear and biological weapons, increasing the potential for worldwide catastrophe.

1910-1920: In Russia, the Bolsheviks, led by Vladimir Lenin, seize power and proclaim Russia a Soviet Federated Socialist Republic.

Today: Having largely abandoned communism, Russia makes steps towards a full-fledged democracy and market economy.

1910-1920: Expressionist literature, drama, and art dominate the avant-garde in Europe, shocking audiences and viewers in its departure from Realism.

Today: The capacity of art and literature to shock is largely gone, and no one movement or approach dominates. Instead of shock, readers and viewers often feel boredom in response to artists'...