Waging war has been the main occupation of man since the first recorded civilizations.

According to the Oxford English Dictionary, “war” is defined as

  • A state of armed conflict between different countries or different groups within a country.
  • A state of competition or hostility between different people or groups.
  • A sustained campaign against an undesirable situation or activity.

The deadliest war in history, in terms of the cumulative number of deaths since its start, is World War II, from 1939 to 1945, followed by the Mongol conquests at up to 50 million. Three of the ten most costly wars, in terms of loss of life, have been waged in the last century. These are the two World Wars, followed by the Second Sino-Japanese War (which is sometimes considered part of World War II, or as overlapping). Most of the others involved China or neighboring peoples.

World War II cost the most human life, fatalities numbering 56.4 million including civilians. Poland lost 6 million (17% of their population). Four out of five Russian men born in 1923 were killed in World War II.

August 6, 1945 the US dropped and atomic bomb on Hiroshima killing over 130,000. Another 25,200 died from radiation within the next year. Approximately 83,000 people were killed in Tokyo, Japan on March 10, 1945.

The Battle of Somme, France claimed 1.22 million casualties (dead and wounded). The highest death toll of 1.1 million in the Battle of Stalingrad. Of this total, only 1,515 civilians of an original 500,000 survived.

As far as civil wars are concerned, the Taiping Rebellion that occurred between 1851 and 1864 against the Qing dynasty in China was responsible for 20 million deaths.

Killers and fanatics are more modest contributors. An Indian Thug named Behram strangled at least 931 victims in the Oudh district from 1790 to 1840. Possibly as many as 2 million Indians were strangled by the Thuggee cult between 1550 and 1853.

Why Do Wars Happen?

Wars have been a part of human history for thousands of years, and have become increasingly destructive as industrialization and technology have advanced.

There is rarely one single, clear cause of conflict and, ultimately, war. The causes of a war are usually numerous and can often be intertwined in a complicated way.

Many theories have been put forth over the years as to why wars happen, and some of the greatest minds have offered their take on the subject.

Eight Main Causes of War

  1. Economic Gain
  2. Territorial Gain
  3. Religion
  4. Nationalism
  5. Revenge
  6. Civil War
  7. Revolutionary War
  8. Defensive War

According to Carl von Clausewitz, war is nothing but a duel on an extensive scale…’ an act of violence intended to compel our opponent to fulfill our will,’ directed by political motives and morality. (Clausewitz 1940: Book I, Ch. I).

Clausewitz acknowledged the link between war and politics, ‘War is nothing more than the continuation of politics by other means… For political aims are the end and war is the means, and the means can never be conceived without the end.’ The greater the motives for war, the more the existence of the entire nation is concerned, and the more violent the tension will be which precedes the war.

War is neither a scientific game nor an international sport; it is an act of violence, characterized by destruction. According to Clausewitz, war is always limited by ‘friction’ – uncertainty, chance, and inevitable logistical or organizational misfortunes. Also mentioned is the notion of ‘rational calculus,’ that states intrinsically use violence to achieve a desired end. The less controlled the use of violence is by one side, the lengthier the war.

More on Clausewitz

List of major wars

Ancient wars (Before 500 AD)

Conquests of Cyrus the Great100,000+549 BC–530 BCPersian Empire vs. various statesMiddle East
Greco–Persian Wars300,000+499 BC–449 BCGreek City-States vs. Persian EmpireGreece
Samnite Wars33,500+343 BC–290 BCRoman Republic vs. SamnitesItaly
Wars of Alexander the Great142,000+336 BC–323 BCMacedonian Empire and other Greek City-States vs. various statesMiddle East / North Africa / Central Asia / India
Punic Wars1,250,000–1,850,000264 BC–146 BCRoman Republic vs. Carthaginian EmpireWestern Europe / North Africa
First Punic War400,000+264 BC–241 BCRoman Republic vs. Carthaginian EmpireSouthern Europe / North Africa
Second Punic War770,000+218 BC–201 BCRoman Republic vs. Carthaginian EmpireWestern Europe / North Africa
Third Punic War150,000–250,000149 BC–146 BCRoman Republic vs. Carthaginian EmpireTunisia
Kalinga War150,000–200,000262 BC–261 BCMaurya Empire vs. State of KalingaIndia
Qin’s Wars of Unification700,000+230 BC–221 BCQin state vs. Han, Zhao, Yan, Wei, Chu, Qi StatesChina
Cimbrian War410,000–650,000113 BC–101 BCRoman Republic vs. Cimbri and TeutonesWestern Europe
Gallic Wars1,000,000+58 BC–50 BCRoman Republic vs. Gallic tribesFrance
Iceni Revolt150,000+60–61Roman Empire vs. Celtic tribesEngland
Jewish–Roman Wars1,270,000–2,000,00066–136Roman Empire vs. JewsMiddle East/North Africa
First Jewish–Roman War250,000–1,100,00066–73Roman Empire vs. JewsMiddle East
Kitos War440,000+115–117Roman Empire vs. JewsSouthern Europe / North Africa
Bar Kokhba Revolt580,000132–136Roman Empire vs. JewsMiddle East
Gothic War (269)320,000+269Roman Empire vs. GothsEurope
Probus’s German War400,000+277Roman Empire vs. GermansEurope
Gothic War (376–382)40,000+376–382Roman Empire vs. GothsEastern Europe
Three Kingdoms War36,000,000–40,000,000184–280Wei vs. Shu vs. WuChina
Yellow Turban Rebellion3,000,000–7,000,000184–205Peasants vs. Eastern Han ChinaChina
Wars of the Sixteen Kingdoms150,000+
304–439Northern Chinese StatesNorthern China
Hunnic Reclaims165,000+
395–453Roman Empire vs. Hunnic EmpireEurope

Medieval wars (500–1500 AD)

Arab–Byzantine Wars2,000,000+629–1050Byzantine Empire and allies vs. Islamic Empire and AlliesMiddle East / North Africa / Southern Europe
Reconquista7,000,000-10,000,000711–1492Spanish and Portuguese states vs. Muslim statesIberian Peninsula
Goguryeo–Sui War300,000+598–614Sui Dynasty China and Goguryeo KingdomChina, Korea
An Lushan Rebellion13,000,000–36,000,000755–763Tang Dynasty China and Islamic Empire vs. Yan stateChina
Goryeo–Khitan Wars90,000+993–1019Liao Empire vs. Goryeo KingdomKorea
Song–Đại Việt war600,000+1075–1077Song Empire vs. Dai Viet Kingdom under Lý dynastyChina, Vietnam
Crusades1,000,000–3,000,0001095–1291Originally Byzantine Empire vs. Seljuq Empire, but evolved into Christians vs. Muslims.Europe / Middle East (“Holy Land”)
Albigensian Crusade200,000–1,000,0001208–1229Papal States and France vs. Cathartic StatesFrance
Mongol invasions and conquests30,000,000–40,000,0001206–1368Mongol Empire vs. Several Eurasian statesEurasia
Wars of Scottish Independence60,000–150,0001296–1357Scotland vs. EnglandScotland / England
Hundred Years’ War2,300,000–3,300,0001337–1453House of Valois vs. House of PlantagenetWestern Europe
Conquests of Timur8,000,000–20,000,0001370–1405Timurid Empire vs. several middle eastern statesEurasia
Wars of the Roses35,000–105,0001455–1487House of Lancaster, House of Tudor, and allies vs. House of York and alliesEngland / Wales

Pre modern (1500 AD–2000) wars with greater than 25,000 deaths

Italian Wars300,000–400,0001494–1559Holy Roman Empire, Spain, and some Italian States vs. France, Ottoman Empire, and some Italian statesSouthern Europe
Spanish conquest of the Aztec Empire2,300,000+1519–1632Spanish Colonial Empire vs. Aztec EmpireMexico
Spanish conquest of Yucatán1,460,000+1519–1595Spanish Colonial Empire vs. Mayan StatesNorth America
Spanish conquest of the Inca Empire8,400,000+1533–1572Spanish Colonial Empire vs. Inca EmpirePeru
Campaigns of Suleiman the Magnificent200,000+1521–1566Ottoman Empire vs. several Balkan, African, and Arabian StatesEastern Europe / Middle East / North Africa
German Peasants’ War100,000+1524–1525German Peasants vs. Swabian LeagueGermany
French Wars of Religion2,000,000–4,000,0001562–1598Protestants vs. France vs. CatholicsFrance
Eighty Years’ War600,000–700,0001568–1648Dutch Republic, England, Scotland, and France vs. Spanish EmpireWorldwide
Anglo-Spanish War (1585–1604)138,285+1585–1604Spanish Empire and allies vs. Kingdom of England and alliesEurope / Americas
Japanese invasions of Korea1,000,000+1592–1598Kingdom of Great Joseon and Ming China vs. JapanKorea
Nine Years’ War (Ireland)130,000+1593–1603Irish rebels vs Kingdom of EnglandIreland
Transition from Ming to Qing25,000,000+1616–1683Qing China vs. Ming China vs. Shun dynasty China (Li Zicheng) vs. Xi dynasty China (Zhang Xianzhong vs. Kingdom of Shu (She-An Rebellion) vs. Evenk-Daur federation (Bombogor)China
Thirty Years’ War4,000,000–12,000,0001618–1648Pro-Habsburg states vs. Anti-Habsburg statesEurope
Franco-Spanish War (1635–1659)200,000+1635–1659France and Allies vs. Spain and AlliesWestern Europe
Wars of the Three Kingdoms876,000+1639–1651Royalists vs. Covenanters vs.Union of the Irish vs. Scottish Protestants vs. ParliamentariansBritish Isles
English Civil War211,830+1642–1651Royalists vs. ParliamentariansEngland, Scotland, and Ireland
Deluge3,000,0001655–1660 Primarily Poland vs. Sweden and RussiaPoland
Mughal–Maratha Wars5,000,000+1658–1707Maratha empire vs. Mughal EmpireIndia-Bangladesh
Franco-Dutch War342,0001672–1678France and allies vs. Dutch Republic and alliesWestern Europe
Great Turkish War380,000+1683–1699Ottoman Empire vs. European Holy LeagueEastern Europe
Nine Years’ War680,000+1688–1697France vs. League of Augsburg (Dutch, Habsburgs, England, Scotland, Spain and others)Global (mainly Europe)
Great Northern War350,000+1700–1721Russia and allies vs. Swedish EmpireEastern Europe
War of the Spanish Succession400,000–1,250,0001701–1714Grand Alliance vs. Bourbon AllianceEurope / Americas
Maratha expeditions in Bengal400,000+1741–1751Maratha Empire vs. Nawab of BengalIndia, Bangladesh
Seven Years’ War868,000–1,400,0001756–1763Great Britain and allies vs. France and AlliesWorldwide
Sino-Burmese War70,000+1765–1769Burma vs. Qing ChinaSoutheast Asia
Tây Sơn rebellion1,200,000–2,000,000+1771–1802Tây Sơn rebels then dynasty (British supports) and Chinese pirates vs Nguyễn lords, Trịnh lords, Lê dynasty of Vietnam; Siam; Qing dynasty of China; Kingdom of Vientiane; French army.Southeast Asia
American Revolutionary War70,000-116,0001775–1783United States and allies vs. British Empire and German MercenariesWorldwide
White Lotus Rebellion100,000+1794–1804Qing China vs. White Lotus rebelsChina
French campaign in Egypt and Syria65,000+1798–1801France vs. Ottoman Empire and Great BritainMiddle East / North Africa
Saint-Domingue expedition135,000+1802–1803France vs. Haiti and UKHaiti
Napoleonic Wars3,500,000–7,000,0001803–1815Coalition powers vs. French empire and alliesWorldwide
French invasion of Russia540,000+1812French Empire vs. RussiaRussia
Spanish American wars of independence600,000+1808–1833Spain and Portugal vs. American IndependentistsAmericas
Venezuelan War of Independence228,000+1810–1823Spain vs. Venezuelan statesVenezuela
Mfecane1,000,000–2,000,0001810s–1840sEthnic communities in southern AfricaModern day South Africa
Carlist Wars200,000+1820–1876Carlist Insurgents vs. SpainSpain
Greek War of Independence170,000+1821–1831Greek Revolutionaries vs. Ottoman EmpireGreece
French conquest of Algeria480,000–1,000,0001830–1903France vs. Algerian resistanceAlgeria
Taiping Rebellion20,000,000–70,000,0001850–1864Qing China vs. Taiping Heavenly KingdomChina
Crimean War356,000–615,0001853–1856Ottoman Empire and allies vs. RussiaCrimean Peninsula
Red Turban Rebellion (1854–1856)1,000,000+1854–1856Qing China vs. Red Turban rebelsChina
Miao Rebellion4,500,0001854–1873Qing China vs. MiaoChina
Punti–Hakka Clan Wars500,000–1,000,000+1855-1868Hakka vs. PuntiChina
Panthay Rebellion890,000–1,000,0001856–1873Qing China vs. HuiChina
Indian Rebellion of 1857800,000–1,000,0001857–1858Sepoy Mutineers vs. British East India CompanyIndia
American Civil War650,000–1,000,0001861–1865Union States vs. Confederate StatesUSA
Dungan Revolt8,000,000–20,000,0001862–1877Qing China vs. Hui vs. KashgariaChina
French intervention in Mexico49,287+1862–1867Mexican Republicans vs. France and Mexican EmpireMexico
Paraguayan War300,000–1,200,0001864–1870Triple alliance vs. ParaguaySouth America
Austro-Prussian War40,000+1866Austrian states vs. German statesCentral Europe
Ten Years’ War241,000+1868–1878Spain vs. CubaCuba
Franco-Prussian War433,571+1870–1871France vs. German statesFrance and Prussia
Conquest of the Desert30,000–35,0001870s–1884Argentina vs. Mapuche peoplePatagonia
Aceh War97,000–107,0001873–1914Kingdom of the Netherlands vs. Aceh SultanateIndonesia
First Sino–Japanese War48,311+1894–1895Qing China vs. JapanEast Asia
Cuban War of Independence362,000+1895–1898USA and Cuba vs. SpainCuba
War of Canudos30,000+1896-1897First Brazilian Republic vs. Canudos inhabitantsBrazil
Thousand Days’ War120,000+1899–1902Colombian Conservatives vs. Colombian LiberalsColombia
Boxer Rebellion100,0001899–1901Boxers vs. Foreign powersChina
South African War (Second Boer War)73,000–90,0001899-1902United Kingdom and allies vs. South African Republic and Orange Free StateSouth Africa
Philippine–American War234,000+1899–1912Philippines vs. USAPhilippines
Russo-Japanese War101,300–206,1001904–1905Russia vs. JapanNortheast Asia
Mexican Revolution500,000–2,000,0001910–1920In reality, a full blown Civil War with multiple sidesMexico
1911 Revolution220,0001911Qing China vs. RevolutionariesChina
Balkan Wars140,000+1912–1913Serbia, Montenegro and Bulgaria against the Ottoman EmpireBalkan Peninsula
World War I16,000,000–40,000,000+ (the higher estimate also includes the first victims of the related Spanish flu epidemic who died by the end of 1918. Neither includes the subsequent Russian Civil War)1914–1918Allied Powers vs. Central PowersWorldwide
Russian Civil War5,000,000–9,000,0001917–1922Red army and allies vs. White army and alliesRussia
Kurdish separatism in Iran15,000–58,0001918–presentQajar dynasty vs. Shekak (tribe)Iran
Iraqi–Kurdish conflict138,800–320,1001918–2003Kurdistan/Iraqi Kurdistan and allies vs. Iraq and alliesIraq
Rif War30,500+1921–1926Spain vs. Republic of the RifMorocco
Kurdish–Turkish conflict100,000+1921–presentTurkey vs. Kurdish peopleMiddle East
Second Italo-Senussi War40,000+1923–1932Italy vs. Senussi OrderLibya
Chinese Civil War8,000,000–11,692,0001927–1949ROC vs. PRCChina
Chaco War85,000–130,0001932–1935Bolivia vs. ParaguayGran Chaco
Second Italo–Ethiopian War278,000+1935–1936Ethiopian Empire vs. ItalyEthiopia
Spanish Civil War500,000–1,000,0001936–1939Nationalists vs. RepublicansSpain
Second Sino-Japanese War20,000,000–25,000,0001937–1945Republic of China and allies vs. JapanChina
World War II85,000,0001939–1945Allied powers vs. Axis PowersWorldwide
Winter War153,736–194,8371939–1940Finland vs. Soviet UnionFinland
Greco-Italian War27,000+1940–1941Greece vs. ItalySoutheast Europe
Continuation War387,300+1941–1944Finland and Germany vs. Soviet UnionNorthern Europe
Soviet–Japanese War33,420–95,7681945Soviet Union and Mongolia vs. JapanManchuria
First Indochina War400,000+1946–1954France vs. Việt Minh, Lao Assara, and Khmer IssarakSoutheast Asia
Partition of India200,000–2,000,0001946–1948India and PakistanSouth Asia
Greek Civil War158,000+1946–1949Greek Government army vs. DSEGreece
Malagasy Uprising11,342–89,0001947–1948France vs. Malagasy InsurgentsMadagascar
Kashmir conflict80,000–110,0001947–presentIndia vs. PakistanNorth India / Pakistan
La Violencia192,700–194,7001948–1958Colombian Conservative Party vs. Colombian Liberal PartyColombia
Internal conflict in Myanmar130,000–250,0001948–presentMyanmar vs. Burmese Insurgent GroupsMyanmar
Arab–Israeli conflict116,074+1948–presentArab Countries vs. IsraelMiddle East
Annexation of Hyderabad29,000–242,0001948Dominion of India vs. HyderabadIndia
Korean War1,500,000–4,500,0001950–1953South Korea and allies vs. North Korea and alliesKorea
Algerian War400,000–1,500,0001954–1962Algeria vs. FranceAlgeria
Ethnic conflict in Nagaland34,000+1954–presentIndia and Myanmar vs. Naga PeopleNortheast India
Vietnam War1,300,000–4,300,0001955–1975South Vietnam and allies vs. North Vietnam and alliesVietnam
First Sudanese Civil War500,000+1955–1972Sudan vs. South Sudanese RebelsSudan
Congo Crisis100,000+1960–1965DRC, USA, and Belgium vs. Simba and Kwilu RebelsCongo
Angolan War of Independence83,000–103,0001961–1974Angola vs. Portugal and South AfricaAngola
North Yemen Civil War100,000–200,0001962–1970Kingdom of Yemen and Saudi Arabia vs. Yemen Arab Republic and United Arab RepublicYemen
Mozambican War of Independence63,500–88,5001964–1974FRELIMO vs. PortugalMozambique
Insurgency in Northeast India25,000+1964–presentIndia and allies vs. Insurgent GroupsNortheast India
Colombian conflict220,000+1964–presentColombia and allies vs. Far Left guerillas and Far Right paramilitaresColombia
Nigerian Civil War1,000,000–3,000,0001967–1970Nigeria vs. BiafraNigeria
Moro conflict120,000+1969–2019Philippines vs. Jihadist Groups vs. BangsamoroPhilippines
Communist rebellion in the Philippines30,000–43,0001969–presentPhilippines vs. Communist Party of the PhilippinesPhilippines
Bangladesh Liberation War300,000–3,000,000+1971India and Bangladesh vs. PakistanBangladesh
Ethiopian Civil War500,000–1,500,0001974–1991Derg, PEDR, and Cuba vs. Anti-Communist rebel groupsEthiopia
Angolan Civil War504,158+1975–2002MPLA vs. UNITAAngola
Lebanese Civil War120,000–150,0001975–1990Various groupsLebanon
Insurgency in Laos100,000+1975–2007Laos and Vietnam vs. “Secret army” and Hmong peopleLaos
Afghanistan conflict1,400,000–2,000,0001978–presentAfghan mujahideen vs URSS then USAAfghanistan
Kurdish–Turkish conflict45,000+1978–presentTurkey vs. KCKMiddle East
Soviet–Afghan War600,000–2,000,0001979–1989Soviet Union and Afghanistan vs. Insurgent groupsAfghanistan
Salvadoran Civil War70,000–80,0001979–1992El Salvador vs. FMLNEl Salvador
Iran–Iraq War500,0001980–1988Iran and allies vs. Iraq and alliesMiddle East
Internal conflict in Peru70,000+1980–presentPeru vs. PCP-SL and MRTAPeru
Ugandan Bush War100,000–500,0001981–1986ULNF and Tanzania vs. National Resistance ArmyUganda
Second Sudanese Civil War1,000,000–2,000,0001983–2005Sudan vs. South Sudanese rebelsSudan
Sri Lankan Civil War80,000–100,0001983–2009Sri Lanka vs. Tamil TigersSri Lanka
Somali Civil War300,000–500,0001986–presentVarying Somali governments vs. insurgent groupsSomalia
Lord’s Resistance Army insurgency100,000–500,0001987–presentLord’s Resistance Army vs. Central African statesCentral Africa
Nagorno-Karabakh conflict50,000+1988–presentArmenia, Nagorno-Karabakh Separatist forces and allies vs. AzerbaijanAzerbaijan
Gulf War25,500–40,5001990–1991Iraq vs. Coalition ForcesIraq
Algerian Civil War44,000–200,0001991–2002Algeria vs. FIS loyalists vs. GIAAlgeria
Bosnian War97,000–105,0001991–1995Bosnia and Herzegovinian governments and allies vs. Republika Srpska and alliesBosnia
1991 Iraqi uprisings85,000–235,0001991Iraq vs various rebelsIraq
Sierra Leone Civil War50,000–300,0001991–2002Sierra Leone
Burundian Civil War300,000+1993–2005Burundi vs. Hutu rebels vs. Tutsi rebelsBurundi
Rwandan genocide800,000April–July 1994Hutu people vs. Tutsi RebelsRwanda
First Congo War250,000–800,0001996–1997Zaire and allies vs. AFDL and alliesCongo
Second Congo War2,500,000–5,400,0001998–2003Central Africa
Ituri conflict60,000+1999–2003Lendu Tribe vs. Hemu Tribe and alliesCongo

Modern (2000-present) wars with greater than 25,000 deaths

WarDeath rangeDateCombatantsLocation
War on terror272,000–1,260,0002001–presentAnti-Terrorist Forces vs. Terrorist groupsWorldwide
War in Afghanistan (2001–2021)212,191+2001–2021Afghanistan
Iraq War405,000–654,9652003–2011Iraq vs USAIraq
War in Darfur300,000+2003–presentSRF and allies vs. Sudan and allies vs. UNAMIDSudan
Kivu Conflict100,000+2004–presentsee Kivu ConflictCongo
Insurgency in Khyber Pakhtunkhwa45,900–79,0002004–2017Pakistan, USA, and UK vs. Terrorist groupsPakistan
Mexican drug war150,000–250,0002006–presentMexico vs. Drug cartelsMexico
Boko Haram insurgency350,000+2009–presentMultinational Joint Task Force vs. Boko HaramNigeria
Syrian civil war499,000–610,000+2011–presentSyrian Arab Republic vs. Republic of Syria vs. ISIL vs. Syrian Democratic ForcesSyria
Rojava–Islamist conflict50,000+2013–presentSyrian Democratic Forces vs. Islamic States of Iraq and Levant vs. al-Nusra FrontSyria
War in Iraq (2013–2017)195,000–200,000+2013–2017Iraq and allies vs. ISILIraq
Yemeni Civil War377,000+2014–presentYemen’s Supreme Political Council vs. Hadi Government, Saudi-led Coalition and the UAE-backed Southern Movement vs Al-QaedaYemen
Russo-Ukrainian War23,000–200,0002014–presentRussia vs. UkraineUkraine
Tigray War300,000–500,000 2020–presentUFEFCF vs. Ethiopian and Eritrean GovernmentEthiopia (Tigray, Afar and Amhara Regions)
To be continued …