Dating 20th century
Technological advancements during World War I changed the way war was fought, as new inventions such as tanks, chemical weapons, and aircraft modified tactics and strategy.
After more than four years of trench warfare in western Europe, and 20 million dead, the powers that had formed the Triple Entente (France, Britain, and Russia, later replaced by the United States and joined by Italy and Romania) emerged victorious over the Central Powers (Germany, Austria-Hungary, the Ottoman Empire and Bulgaria).
Mass media, telecommunications, and information technology (especially computers, paperback books, public education, and the Internet) made the world's knowledge more widely available.
Advancements in medical technology also improved the health of many people: the global life expectancy increased from 35 years to 65 years.
Meanwhile, Western European countries were influenced by the American Marshall Plan and made a quick economic recovery, becoming major allies of the United States under capitalist economies and relatively democratic governments. When the conflict ended in 1945, the United States and the Soviet Union emerged as the major world powers.
It is distinct from the century known as the 1900s (sometimes written as 19XX), which began on January 1, 1900 and ended on December 31, 1999.Meanwhile, Japan had rapidly transformed itself into a technologically advanced industrial power.Its military expansion into eastern Asia and the Pacific Ocean culminated in a surprise attack on the United States, bringing it into World War II.Terms like ideology, world war, genocide, and nuclear war entered common usage.Scientific discoveries, such as the theory of relativity and quantum physics, profoundly changed the foundational models of physical science, forcing scientists to realize that the universe was more complex than previously believed, and dashing the hopes (or fears) at the end of the 19th century that the last few details of scientific knowledge were about to be filled in.