In 1914, a Serbian political extremist murdered Austrian Archduke Franz Ferdinand. The murder caused an avalanche of political repercussions that culminated in World War I.

In 1765, the British levied a ridiculous Stamp Act on its New World colonies, essentially taxing colonists for many everyday printed materials.

In June 1950, North Korea invaded South Korea, and the United Nations rushed to the South's defense. Then, China jumped into the fray with the North. And a long, bloody war began.

In September 1939, Hitler's troops spilled over into Poland. Within a month, the Third Reich took control of the country, and the European Theater of WWII was in full swing.

The terrorist attacks of September 11, 2001 led to a snowball effect that found American troops in Afghanistan. And they are still there -- this war will likely go down as the longest in American history.

In December 1941, Japan's navy attacked Pearl Harbor, drawing the United States into combat that it had hoped to avoid. The Pacific Theater of the war eventually revealed some of the ugliest sides of human nature.

As part of its war against France, Britain often seized American civilian sailors and forced them to fight alongside British men. The act was called impressement, and it caused major resentment in the United States.

The issue of slavery was a major contributor to the Civil War. In the North, anti-slavery view held sway -- in the South, slavery was an integral part of the agrarian culture. The two sides could not exist in the same Union.

In the so-called Gleiwitz incident, German operatives staged an attack on a German radio station, making it look as though Polish troops were responsible. Hitler used the faked attack as justification for his invasion of Poland.

America was sure that communism was going to spread throughout all of Southeast Asia, but decided to stop it in its tracks in Vietnam. Although the U.S. lost the war, some historians say American actually succeeded in its efforts to stop communism from gaining a wider range.

In 2003, the Bush Administration presented information that it said proved that Iraq had weapons of mass destruction that it could use for a variety of nefarious purposes. The U.S. invaded … and never found the infamous WMDs.

In the 1930s, Hitler began annexing portions of Europe and adding them to Germany territory. Other powers appeased Hitler instead of confronting him, in effect giving the Nazis momentum in their imperialstic craze.

After WWII, much of the Western world feared the spread of communism. The U.N. and U.S. jumped to help South Korea in hopes of stemming a red tide from consuming the Korean peninsula.

The Cold Was was a standoff between East and West, communism and democracy, and it resulted in proxy wars between countries like the U.S. and communist nations. The Vietnam War was one such war.

In 1990, Iraq invaded Kuwait and saw immediate backlash from the international community. A huge military coalition, led by the U.S., pushed Iraq back and demolished much of the country's army.

The Treaty of Versailles ended WWI but levied incredible (and humiliating) terms on Germany. Even before the ink had dried, many politicians knew the treaty would cause another war.

With France and Britain at war, both sides tried to interfere with each others' trade with America. The tumult increased hostilities between Britain and the U.S.

In March 1770, a Boston mob clashed with British troops, who fired wildly into the crowd, killing several people. The Boston Massacre added to the revolutionary fervor that gripped the colonies.

In the late 1920s, Germany's economy (like many others during the Great Depression) was in a full tailspin. Widespread impoverishment gave Hitler a desperate audience who gobbled up his violent and racist rhetoric.

America and its allied created a "containment" policy meant to keep Communism from spreading to countries around Vietnam. They backed up that policy with a lot of bullets and bombs.

Prior to WWI, Europe was a complicated tangle of mutual defense alliances. All it took was one act of aggression, and suddenly countries were oblligated to spring to each others' defense.

In the 1840s, the U.S. was rapidly settling the West … and President Polk wanted even more land to add to his legacy. The Mexican-American War gave him the opportunity to do just that.

Starting in the 1330s, the Hundred Years' War was sparked by complex political clashes between Britain and France. The war dragged on until 1453.

As the Industrial Revolution gripped Europe, Germany -- with its limited natural resources -- began to fall behind France and Britain. It joined the fight in part to acquire new territory and new natural natural resources.

The Thirty Years' War had much of its basis in conflicts between Catholics and Protestants. The war started in 1618 and killed millions of people across Europe.

Around the turn of the century, Japan's power structure swung towards the military, which took on great importance throughout the country. Japanese militarism contributed heavily to the start of WWII.

The British crown made a habit of taxing the New World colonies, but didn't allow colonists equal representation in their government. "No taxation without representation" became a rallying cry for the rebels of the Revolution.

At the start of the 20th century, European nations were essentially in an arms race, rapidly building their militaries and creating strategies to use them. It was only a matter of time before they took the opportunity to do so.

In the 1700s, Britain and France raced each other to claim lands in North America. Their territorial claims and political clashes resulted in the French and Indian War, with the Americans fighting alongside the British.

Fought in the 1850s, the Crimean War was had its roots in religious clashes, particularly with regard to Christians and their treatment in the Holy Land. An Allied victory resulted in the Treaty of Paris of 1856.