In 1900, the countries of the West (Great Britain, France, United States, Germany were the richest, most powerful, and technologically advanced in the world. Empires, trade, and influence reached around the globe. Few would have believed the world was facing 50 years of war and turmoil.

Why did so many upheavals occur during this brief period of history? The answer lies partly in the rapid changes that took place everywhere. In particular, national and economic rivalries led to the two world wars.

Wars often create more problems than they solve. In Europe, World War I opened the door to revolution and communism in Russia. War also opened the way for totalitarianism in Germany and Italy. The two governments had total control over their citizens. They were nationalistic dictatorships that used terror and murder to protect the rule of a single party. When these countries tried to expand their empires, tensions exploded into World War II.

Meanwhile, the idea of national independence spread in Asia, Africa, and the Middle East. In these areas, strong resentment was building up against imperialism, that is, the rule or authority of one country over other countries or colonies. Everywhere, nationalism became the single most powerful force of the 20^th century. It, more that anything else, explains why the world has been in upheaval for so much of the 20^th century and into the 21^st.