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15. Reconquista -

The Reconquista was a drawn-out campaign spanning from 718 to 1492, during which Christian kingdoms in the Iberian Peninsula gradually reclaimed territory from Muslim rulers. The battlefront shifted over centuries, marked by sieges, truces, and bursts of bloodshed.

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15. Reconquista -

Though the death toll hovered around seven million, the Reconquista reshaped Spanish identity and Europe’s religious landscape. Its culmination in 1492 with the fall of the Spanish city of Granada also signaled the dawn of Spain’s imperial ambitions.

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14. Spanish conquest of the Inca Empire -

The Spanish conquest of the Inca Empire was a short yet catastrophic campaign beginning in 1532, when Francisco Pizarro’s small force overthrew the massive Incan civilization, aided by internal divisions and foreign disease.

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14. Spanish conquest of the Inca Empire -

By the end of the conflict in 1572, over eight million lives had been lost due to a combination of bloodshed, enslavement, famine, and introduced epidemics. The fall of the Inca Empire is considered one of the most tragic collapses in indigenous American history.

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13. Thirty Years' War -

The Thirty Years’ War from 1618 to 1648 was fueled by a volatile mixture of Catholic-Protestant religious conflicts and dynastic rivalries, all of which eventually spiraled into one of Europe’s most devastating continental wars.

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13. Thirty Years' War -

Over eight million people perished (mostly civilians) as scorched-earth tactics, famine, and disease ravaged the Holy Roman Empire. The war forever altered Europe’s political landscape and gave rise to the modern concept of state sovereignty.

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12. Crusades -

The Crusades, spanning from 1096 to 1291, were religious wars sanctioned by the Latin Church against Muslims, aimed at reclaiming Jerusalem and the Holy Land from Muslim rule. The Church’s motives, however, quickly expanded beyond religion.

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12. Crusades -

With a death toll of nearly nine million, the Crusades saw horrifying massacres and introduced centuries of distrust between Christians and Muslims. The brutality on both sides shaped centuries of Christian-Muslim relations across continents and can still be felt generations later.

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11. Chinese Civil War -

The Chinese Civil War (1927–1949) was a violent ideological conflict between the Kuomintang-led nationalist government and Mao Zedong’s Communist forces. The war was only briefly interrupted when China led a united front against Japan in World War II.

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11. Chinese Civil War -

Claiming the lives of roughly 10 million people, the civil war’s toll rose through famine, purges, and widespread atrocities. The war ultimately ended with the Communists' victory and the establishment of the People’s Republic of China in 1949.

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10. Russian Civil War -

The Russian Civil War (1917–1923) erupted after the fall of the Romanov dynasty during the October Revolution. The Bolshevik Red Army was pitted against the anti-communist White forces, alongside anarchists, nationalists, and foreign interventionists battling across vast territories.

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10. Russian Civil War -

With nearly 12 million deaths caused by battle, famine, and disease, the civil war ended with the Red Army’s dominance. This marked the birth of the Soviet Union and decades of authoritarian rule before the USSR was dissolved in 1991.

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9. Spanish conquest of Mexico -

The Spanish conquest of Mexico began in 1519 when Hernán Cortés, with only a few hundred soldiers, turned indigenous allies against the mighty Aztec Empire, which had stood for nearly 200 years. The war ultimately led to the fall of the empire’s capital city, Tenochtitlan, by 1521.

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9. Spanish conquest of Mexico -

An estimated 12 million people died due to slaughter, forced labor, and disease. The Aztec Empire was obliterated, and its spiritual, political, and cultural heart was replaced by the emerging colonial power of New Spain.

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8. An Lushan rebellion -

The An Lushan Rebellion (755–763) was one of China’s most catastrophic internal uprisings. The rebellion was led by a discontented general of foreign descent, and it ignited a civil war that shattered the Tang Dynasty’s power, triggering one of the deadliest conflicts in Chinese history.

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8. An Lushan rebellion -

With over 13 million deaths, the rebellion's impact was catastrophic. It led to massive population loss, economic collapse, and lingering instability, even though the dynasty technically survived for another century.

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7. Conquests of Timur -

In the late 14th century, the Turco-Mongul conqueror known as Timur (or Tamerlane) led a series of brutal military campaigns across Persia, Central Asia, and the Indian subcontinent. For almost 40 years, he claimed Islamic authority while unleashing terror on an epic scale.

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7. Conquests of Timur -

Timur’s conquests left nearly 20 million dead before he was felled by disease in 1405. Cities were razed, civilians slaughtered, and survivors enslaved. Though he built monumental architecture, his empire was steeped in one of history’s darkest legacies of bloodshed.

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6. World War I -

One of the most infamous conflicts in history, World War I (1914–1918) involved more than 30 countries and introduced industrialized warfare on an unprecedented scale. Trench warfare, chemical weapons, and mechanized killing made the battlefield a nightmare, and the home front was wracked by hunger and grief.

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6. World War I -

With roughly 22 million military and civilian casualties, the First World War toppled empires and birthed volatile new nations. Its punitive peace treaties laid the groundwork for political resentment and the next great global war.

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5. Manchu conquest of China -

The Manchu conquest of China (1618–1683) was a prolonged conflict in which the Manchu tribes overthrew the Ming Dynasty and established the Qing Dynasty. The transformation was rooted in military strategy, betrayal, and mass slaughter.

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5. Manchu conquest of China -

More than 25 million people died during the 65-year conflict, including civilians caught in mass executions and famines. The conquest sealed the Manchu’s rule over China for over 250 years, and left deep cultural and ethnic scars.

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4. Taiping Rebellion -

The Taiping Rebellion (1850–1864) was led by a Chinese revolutionary and religious leader named Hong Xiuquan, who claimed to be the brother of Jesus Christ. His millions of followers sought to overthrow the Qing Dynasty and create a heavenly kingdom on Earth.

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4. Taiping Rebellion -

Approximately 30 million perished during the rebellion, making it one of history’s deadliest conflicts. Brutal campaigns, scorched cities, and internal purges reduced vast swathes of China to rubble, leaving the Qing weakened and society in ruins.

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3. Three Kingdoms -

The Three Kingdoms refers to a period between 184 and 280 CE following the collapse of the Han Dynasty, at which point China was divided into the rival states of Wei, Shu, and Wu. Power struggles and shifting alliances fueled near-continuous warfare for decades.

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3. Three Kingdoms -

An estimated 36 to 40 million people died during this violent fragmentation. Although it has since been romanticized in Chinese folklore, the era was marked by profound suffering, famine, and a collapsing imperial infrastructure.

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2. Mongol invasions and conquests -

Between 1206 and 1368, the Mongol invasions saw Genghis Khan and his successors launch vast, coordinated military campaigns across Eurasia, subjugating entire civilizations with psychological warfare, tactical brilliance, and merciless slaughter.

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2. Mongol invasions and conquests -

An estimated 40 to 60 million people died as the Mongols razed cities, rerouted trade, and exterminated populations. Their conquests created the largest contiguous empire in history, but at a horrifying human cost.

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1. World War II -

World War II is largely considered the deadliest war in history, simply due to its death toll. The war, which took place between 1939 and 1945, erupted from fascist Nazi aggression, economic instability, and even unresolved tensions from World War I. It became the first truly global conflict, involving air, sea, and land battles across six continents.

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1. World War II -

An estimated 70 to 85 million people perished in the Second World War. Genocides, atomic bombings, and unprecedented civilian casualties marked this as the deadliest war ever, leaving behind a fragile peace and a reshaped international order.

Sources: (Our World in Data) (Britannica) (Military Wiki) (Encyclopedia)

See also: The deadliest passenger plane crashes ever

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