The Italian "Il Duce" had one of the most dramatic transformations of any politician in history. An ardent socialist for the first three decades of his life, he abruptly left the party and developed his own brand of nationalist.
Il Duce's ineffective economic policies left Italy completely unprepared for World War II, and yet he forced the country into it anyway. What followed was a defeat so embarrassing that it remains legendary for its incompetency to this day.
Before he became the leader of one of the most powerful countries in the world, Joseph Stalin was an idealistic, but ruthless revolutionary. A Marxist from a young age, he devoted much of his life to overthrowing Imperial Russia.
Joseph Stalin went on to transform the Soviet Union into a modernized country but at the cost of millions of lives. In order to fulfill his vision of communism, the deaths of peasants and political enemies were required.
As a young man, nobody would have expected aspiring artist Adolf Hitler to become one of history's cruelest dictators. But once he realized he had a talent for politics, Hitler began a lifelong quest for absolute power.
Ivan Vasilyevich the Fourth was crowned Grand Prince of Muscovy at 3 years old after his father died. After a traumatic childhood of chaos and coups, Ivan would crown himself the first Tsar of Russia and go on to create the Russian Empire.
After the death of his beloved first wife, Tsar Ivan the Terrible descended into madness and paranoia. He turned his hatred and fear against his own people dragging the empire he had built with his own hands down into poverty and despair.
A nomad exiled from his tribe as a child, Genghis Khan used populism and meritocracy to unite the tribes of the Mongolian Steppe and become the ruler of all of Mongolia from 1206-1227 CE.
After uniting the Mongol tribes in 1206, Genghis Khan used his military prowess to assert dominance over the Ottoman Empire and the Chinese Jin Dynasty. By 1222, his empire spanned from the Caspian Sea to the Pacific Ocean.
Born between 1428-1431, Vlad the Impaler was abandoned by his father as a boy and betrayed by everyone he trusted. He channeled his resentment into an unquenchable lust for power and violence-eventually becoming the ruler of Wallachia.
Purged Wallachia of enemies and retained an iron grip on power in the region. But as Vlad the Impaler's power expanded, so did his violent, paranoid and psychotic behavior until he alienated everyone around him and was violently deposed.
How did Manuel Noriega rise from nothing to become the drug-smuggling, secret-selling, military dictator of Panama in the 1980s? He had a great deal of help from the American CIA.
He was the Panamanian politician who ran one of the most successful drug and gun trafficking rings in the world in the 1970s and 80s-until an American coup brought him down.
He rose from anti-Japanese freedom to the leader of a Soviet-led puppet government in North Korea. But just as North Korea gained its independence, Kim Il-sung led the country to the brink of extinction, by dragging it into a civil war.
In the aftermath of the Korean War, Kim Il-sung used propaganda and violence to exert total control of North Korea and its people-transforming it into the most isolated nation on earth.
Born in a guerilla camp in the early 1940s, Kim Jong-il seemed destined to take his father's place. Under the grooming of his father, Kim Il-sung, Kim Jong-il experienced a meteoric rise through North Korea's communist ranks.
After carrying the legacy of his father into the 1990s, Kim Jong-il took a defensive stance against the world, isolating North Korea from global affairs.
For the first two decades of his life, the world was unaware of the existence of Kim Jong-un. Hidden in the penthouses of Pyongyang and educated in Europe, was introduced to the world as his father's successor in the late 2000s.
Growing up in colonial Uganda in the 1930s and '40s, Idi Amin chose to embrace his British colonists by joining the British Army. Climbing the ranks, he became a natural choice to lead the Ugandan Army after independence.
His early life, before seizing power in 1968, is shrouded in mystery. But what do know is that Francisco Macias Nguema used the colonial system as a means to grasp his own power.
In a move inspired by his hero, Napoleon, Bokassa named himself Emperor of the Central African Republic in 1977. But his lavish spending and absolute rule drew the ire of the nation's students.
In 1976, after thirty years as a military officer, Videla led a coup against the disastrous President Isabel Perón. He named himself president and waged a brutal war against political opponents and everyday citizens alike.
After establishing himself as a military dictator, Videla fought a bloody conflict against citizens of his own country. With his public perception suffering, he turned to an American advertising agency to help him repair his global image.
He was a career military man until a coup against socialist President Salvador Allende installed him as Chile's next leader. But Pinochet relished his newfound power, and in June 1974, passed a law naming himself the "Supreme Chief".
From 1973 to 1990, Augusto Pinochet ruled over Chile with a brutality that left tens of thousands people missing, tortured, or dead. Despite his atrocities-and an unprecedented arrest-Pinochet escaped conviction for his crimes.
In 1932, 20-year-old Alfredo Stroessner was a cadet at the Paraguayan military academy. It would take a little over two decades for him to seize power through a military coup, and begin his 35-year reign as an implacable autocrat.
All her life, Isabella of France knew she was going to be Queen consort of England. But when her husband took the throne in 1307, it became obvious that he had chosen another as his favorite: Piers Gaveston.
Tired of playing second fiddle, Isabella decided to turn on her husband and join forces with his enemies: the exiled barons. Together, they planned an invasion of England to take the throne from Edward II.
She was never supposed to be queen. But in 1474, when Isabella of Castile's half-brother King Enrique died, she seized her chance to take what was hers.
In the 15th century, Queen Isabella became convinced that heretics and infidels were threatening Christendom. She became the architect of a 300-year-long religious genocide: The Spanish Inquisition.
As the daughter of England's most famous king, Mary Tudor spent much of her life in Henry VIII's shadow, forced to navigate his capricious moods and murderous whims.
This legendary ruler of Rome, known for his wickedness and depravity, was never meant to be emperor. Tiberius came into power in 14 CE only after his adopted father's heirs all died.
In the final years of Emperor Tiberius's reign, he built lavish villas on Capri, hosted orgies with young boys and girls, and tortured and executed people who spoke out against him. He was more than a dictator. He was a monster.
As a child, Caligula lived in the shadow of his father, Germanicus - a hero of Rome. When Germanicus suddenly dies, Caligula is forced to spend his teenage years at the mercy of Emperor Tiberius.
In 37 CE, Caligula became the third emperor of Rome, ushering in a brief era of prosperity before pilfering the treasury and embarking on a quest to conquer Britannia.
He never wanted to be emperor, but his mother Agrippina was determined to put the young Nero on the throne. The boy artist followed her wishes - and led Rome to destruction.
As the Great Fire of Rome wreaked havoc on the city, the emperor practiced his singing. Nero's artistic obsessions led not only to Rome's downfall, but his own.
Before he was a fanatical Nazi doctor, Josef Mengele was a mediocre student studying medicine and anthropology. His quest for renown drove an obsession with human experimentation, and a horrific tenure at Auschwitz-Birkenau.
Before he was a fanatical Nazi doctor, Josef Mengele was a mediocre student studying medicine and anthropology. His quest for renown drove an obsession with human experimentation, and a horrific tenure at Auschwitz-Birkenau.
The Qing Dynasty fell in 1911, ending imperialism in China. But the instability created a power struggle over the country's future. Between the Warlords, the Nationalists, the Communists, and even the Japanese.
Now in total control, Mao Zedong had a nation to build. But his ambition to transform China into a global superpower led to one of the worst crimes ever committed against humanity.
The secretive leader of the communist Khmer Rouge was responsible for killing around a quarter of Cambodia's population - one of the worst mass killings of the 20th century.
Forced labor, unyielding rice quotas, and executions meant to root out anti-communist resistance plunged the country into a terrible nightmare. Pol Pot was finally forced to flee in 1984.