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.

Theodosius II was head of the Eastern Roman Empire when it faced invasions led by Attila the Hun. He became the longest-reigning Roman emperor.

Yangdi was the second and penultimate emperor (604–617/618) of China’s Sui dynasty (581–618).

Wudi was a Chinese emperor who vastly increased the authority of the Han dynasty and extended Chinese influence abroad.

Titus was Roman Emperor from 79-81 AD who--during his short reign--completed the Colosseum and dealt with the eruption of Mount Vesuvius.

Tiberius was an ancient Roman emperor who ruled from year 14 to 37.

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.

Louis I succeeded his father, Charlemagne, as emperor, serving as ruler of the Franks for 26 years.

Leopold II was Holy Roman emperor and one of the most capable of the 18th-century reformist rulers known as the “enlightened despots.”

Leopold I was Holy Roman emperor during whose lengthy reign Austria emerged from a series of struggles to become a great European power.

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.

Henry VI (1165-1197) was a German king and Holy Roman Emperor. He increased the power of his empire by acquiring the kingdom of Sicily.

Henry V served as joint king of Germany with Henry IV until he forced his father to abdicate the throne. Holy Roman emperor from 1111 to 1125, he was the last of the Salian line.

Holy Roman Emperor Henry IV became king of Germany in 1056 and was abdicated in 1105. He overthrew Pope Gregory VII because of conflicts over imperial rule.

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