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Leonidas -

This Spartan king lost his life at the Battle of Thermopylae against the Persians in 480 BCE. Leonidas' army was severely outnumbered but they fought to the death. The story is told in the 2006 movie '300.'

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Archidamus III -

Archidamus III was another king of Sparta who died in battle. He died in 338 BCE at the hands of the Lucanians in the Manduria battle near Tarentum (modern-day Taranto, Italy). 

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Areus I -

After ruling for 44 years, the Spartan king lost his life in battle. Areus I died in 265 BCE near Corinth in the Peloponnese (Greece) during the Chremonidean War against the Macedonians. 

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Gordian II -

The Roman Emperor died in 238 CE after just three years in power. Gordian II lost his life during a Roman civil battle in Carthage (modern-day Tunisia).

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Philip the Arab -

This Emperor of the Roman Empire perished while fighting a rebellion led by Decius in 249 CE. The battle took place in Verona.

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Decius -

Decius went on to become Roman Emperor himself, but he too lost his life in battle. Decius died fighting Goths and Scythians at the Battle of Abritus in 251 CE.

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Maxentius -

Maxentius is yet another Roman Emperor who died during a civil war. The 58th emperor drowned in the Tiber River during the battle of the Milvian Bridge against Constantine in 312 CE.

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Constantine II -

The son of Constantine the Great was killed in 340 CE fighting his brothers in Aquileia. 

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Julian -

The last pagan Emperor of Rome was killed by a Persian soldier in the Battle of Samarra (modern-day Iraq) in 363 CE while fighting the Sasanian Empire.

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Valens -

Eastern Roman Emperor Valens died in 378 CE fighting the Goths in the Battle of Adrianople. 

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Chlodomer -

The King of Franks was the first Western European king to die on the battlefield. Chlodomer was killed in 525 CE fighting the Burgundian army at the Battle of Vézeronce in France.

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Constantine I -

Causantín mac Cináeda, also known as Constantine I, was the king of Scotland aka Alba. He eventually perished after more than a decade fighting the Norsemen. Constantine I met his fate in 877 CE at Inverdovat, Fife. 

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Robert I of France -

Robert I died in 923 CE on the battlefield in Soissons, northern France, against the Carolingian army. 

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Brian Boru -

The High King of Ireland ruled for 12 years before being killed in 1014 in Clontarf, at the hands of Viking mercenaries. The killers were supporting an alliance of Leinstermen and Norsemen from Dublin under the rule of Sitric Silkbeard.

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Harald III Sigurdsson -

Harald the Ruthless was the King of Norway. He died in battle at Stamford Bridge in Yorkshire in 1066 against the English. 

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Harold II -

The Anglo-Saxon King of England, also known as Harold Godwinson, died in 1066. The king died at the hands of the Normans in the Battle of Hastings. 

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William the Conqueror -

After winning the Battle of Hastings, William the Conqueror became the first Norman king of England. He died in 1087 after an injury sustained during a battle against the French in Mantes.

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Antoku, Emperor of Japan -

The Emperor of Japan was only six when he was drowned at sea by force, to avoid being captured by the rival Minamoto clan during the naval Battle of Dan-no-ura in 1185.

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Richard I -

Richard the Lionheart ruled England for a decade but spent most of his time fighting abroad. Richard I died in 1199 from an injury sustained in battle while suppressing a revolt by French nobles in Aquitaine.

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Michael Asen III -

Michael Shishman (second from right) was the Tsar of Bulgaria. He died in 1330 at the hands of the Serbs during the battle of Velbazhd, near modern-day Kyustendil.

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John, King of Bohemia -

The King of Bohemia also known as John of Luxembourg, ruled for 36 years. He met his fate on the battlefield in 1346. John was killed by the English at the Battle of Crécy.

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Murad I -

The Ottoman sultan died in 1389. Murad I was killed by a Serbian noble during the Battle of Kosovo.

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Musa Çelebi -

Musa Çelebi is another sultan of the Ottoman Empire who lost his life on the battlefield. Musa Çelebi died in 1413 at the Battle of Çamurlu against one of his brothers, Mehmet Çelebi. 

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Constantine XI Palaiologos -

The Byzantine Emperor Constantine XI Palaeologos died during the fall of Constantinople in 1453 battling the Ottomans.

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Richard III -

The English king died in 1485 during the Battle of Bosworth, one of the last battles of the War of the Roses. Richard III perished at the hands of Henry Tudor's soldiers. 

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James IV of Scotland -

The Scottish king lost his life in the Battle of Flodden in Northumberland against the English, which took place in 1513. 

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Suleiman the Magnificent -

The Sultan of the Ottoman Empire was 46 years in power. He died from a heart attack in 1566 while sieging Szigetvár in Hungary which was controlled by the Habsburg Empire.

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Sebastian I -

The king of Portugal was just 24 in 1578 when he perished against the Moors in the Battle of the Three Kings in Ksar El Kebir, Morocco.

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Gustavus Adolphus -

The king of Sweden was killed at the Battle of Lützen in 1632. Gustavus Adolphus was fighting the Habsburg Empire.

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Charles XII -

Charles XII was yet another Swedish king who perished in battle. He died in 1718 fighting in Norway after failing to siege the town of Halden. Charles XII was the last European ruler to die in battle.

Sources: (24/7 Wall St.)

See also: Historical rulers who killed family members to gain power

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