Gaius Caesar, known as Caligula, succeeded Tiberius and served as Roman emperor from 37 to 41 A.D.

Napoleon Bonaparte was a military general who became the first emperor of France. His drive for military expansion changed the world.

Mongolian general and statesman Kublai Khan was the grandson of Genghis Khan. After conquering China, he founded the country's Yuan Dynasty and became its first emperor.

As Roman emperor, Nero’s reign was lavish and tyrannical. He killed his mother, persecuted Christians and is said to have "fiddled while Rome burned."

Jean-Jacques Dessalines was a military leader who worked with Toussaint L'Ouverture and gave the country of Haiti its name.

Hirohito was Japan's longest-reigning emperor, holding the throne from 1926 to 1989. He was a controversial figure who announced Japan's surrender to the Allied Forces in 1945.

Napoleon III, the nephew of Napoleon I, was emperor of France from 1852 to 1870. His downfall came during the Franco-Prussian War, when his efforts to defeat Otto Von Bismarck ended in his capture.

Kaiser Wilhelm served as emperor of Germany from 1888 until the end of World War I.

Montezuma II was the last of the Aztec emperors, who was defeated by Spanish conquistador Hernán Cortés in 1520.

Menelik II was king of Shewa and emperor of Ethiopia (1889). He expanded the empire, repelled an Italian invasion, and modernized Ethiopia.

Holy Roman emperor Joseph II tried to strengthen the Habsburg empire with his enlightened reforms, but the changes he made were met with fierce opposition.

Emperor Haile Selassie I worked to modernize Ethiopia for several decades before famine and political opposition forced him from office in 1974.

As Emperor of Rome from 161-180, Marcus Aurelius kept the empire safe from the Parthians and Germans, but is best known for his intellectual pursuits.

Atahualpa was the last Inca ruler, executed by Spanish conquistador Francisco Pizarro in 1533, marking the end of the Inca empire.

Akbar the Great, Muslim emperor of India, established a sprawling kingdom through military conquests, but is known for his policy of religious tolerance.

Caesar Augustus, or Octavian, became the first emperor of the Roman Empire after Julius Caesar died. The country was peaceful under Augustus's rule.

Constantine I was a Roman emperor who ruled early in the 4th century. He was the first Christian emperor and saw the empire begin to become a Christian state.

Peter III was emperor of Russia for a mere six months in 1762 before he was overthrown by his wife, Catherine the Great, and assassinated in 1762.

Charlemagne was the founder of the Carolingian Empire, best known for uniting Western Europe for the first time since the fall of the Roman Empire.