Nationalism is excessive pride in one's nation. A common history, language, race, or religion bind a people together—and exclude outsiders. Nationalism has emerged an an extremely potent force over the past two hundred years.

However, nationalism dates back to antiquity. For example, the ancient Greeks were nationalists. After Alexander the Great conquered Persia in the fourth century BC, he strongly encouraged his officers to marry Persian women. Alexander also admitted Persians into his army. These moves were bitterly opposed by almost all of Alexander's men.

Modern nation-states first developed in the Middle Ages (476 AD–1492). These included France, England, and Spain. These countries were bound together by their monarchs.

The French Revolution, which began in 1793, marked the real beginning of fervent nationalism, however. For the revolutionaries of France, the people were the nation. Kings, princes, and priests were rejected, and the French people were exalted. The intense French nationalism helped Napoleon conquer much of Europe before he was defeated in 1815.

The nineteenth century, then, was the first in which nationalism played a major role. In the United States, nationalism was the driving force in Manifest Destiny—the drive to settle and conquer the West. In Europe, Italian city-states increasingly resented their Hapsburg rulers.

By the mid-nineteenth century, Austria was in trouble. From its majestic capital in Vienna, the Hapsburg dynasty of Austria ruled over a vast multi-ethnic state that included Slavs, Poles, Czechs, Romanians, and many other disparate groups.

A decaying Austria was challenged by a rising Prussia. Prussia, a German state, united all of Germany under its rule by winning wars against Denmark, Austria, and France in 1864, 1866, and 1871, respectively.

By 1871, both Germany and Italy were united. This changed the balance of power in Europe and made other nations on that continent very concerned by German power. Germany had replaced France as the dominant power in Europe.

German nationalism was largely responsible for the two World Wars of 1914–1918 and 1939–1945. Finally, France, Britain, the United States, and the Soviet Union crushed Germany in 1945 and divided the nation. Germany remained divided for nearly fifty years.

Other nations unleashed their nationalism during World War II. Joseph Stalin used propaganda to convince its people that the war against Germany was to save Mother Russia—and not to save Communism. Japan was extremely nationalist and aggressive before it lost WWII.

After WWII ended, nationalism remained a formidable force. For instance, America underestimated the strength of nationalist sentiment in Vietnam during the Vietnam War (1957–1975) and in Iraq during the Iraq War (2003–2011).

Today, there is a struggle between nationalism and multi-national organizations. An example of this conflict is Brexit. In 2016, British nationalists helped convince their countrymen to leave the European Union. Nationalism is a hindrance to solving issues that concern the entire globe—such as global warming.