World war A world war is a war affecting most of the world ' s most powerful and populous countries . World wars span multiple countries on multiple continents , with battles fought in multiple theaters . The term is usually applied to the two conflicts of unprecedented scale that occurred during the 20th century : World War I ( 1914 – 1918 ) and World War II ( 1939 – 1945 ) . However , it is also sometimes applied to earlier wars and to a hypothetical future war . Origins of the term . The term " World War " was coined speculatively in the early 20th century , some years before the First World War broke out , probably as a literal translation of the German word " Weltkrieg " . German writer August Wilhelm Otto Niemann had used the word in the title of his anti - British novel " Der Weltkrieg : Deutsche Träume " ( " The World War : German Dreams " ) as early as 1904 , published in English as " The coming conquest of England " . The " Oxford English Dictionary " cites the first known usage in the English language as being in April 1909 , in the pages of the " Westminster Gazette " . It was recognized that the complex system of opposing alliances — the German Empire , Austria - Hungary , and the Ottoman Empire " vs . " the French Third Republic , the Russian Empire , and the British Empire was likely to lead to a worldwide conflict in the event of war breaking out . The fact that the powers involved had large overseas empires virtually guaranteed that a war would be worldwide , as the colonies ' resources would be a crucial strategic factor . The same strategic considerations also ensured that the combatants would strike at each other ' s colonies , thus spreading the fighting far more widely than in the pre - colonial era . Other languages have also adopted the " World War " terminology ; for instance , in French , the two World Wars are the " Guerres mondiales " ; in German , the " Erste und Zweite Weltkrieg " ( World War I was only known or commonly recognized in public as " der Weltkrieg " in Germany when it was over , while prior to the war the word was used in the more abstract meaning of " a global conflict " ) ; in Italian , the " Guerra Mondiale " ; in Russian the " мировая война " ( " mirovaya voyna " ) ; in Spanish the " Guerra Mundial " and so on . The term " First World War " was used in the book " The First World War : A Photographic History " , edited by playwright and war veteran Laurence Stallings and published in 1933 . The term " World War I " was invented by " Time magazine " magazine in its issue of June 12 , 1939 . In that same issue , the term " World War II " was first used speculatively by " Time " magazine to describe the upcoming war . The first use for the actual war came in its issue of September 11 , 1939 ; one week earlier , the Danish newspaper " Kristeligt Dagblad " used the term on its front page on September 4 , 1939 , saying , " The second World War broke out yesterday at 11 a . m . " Speculative fiction authors were noting the concept of a Second World War at least as early as 1919 and 1920 , when Milo Hastings wrote his dystopia n novel " City of Endless Night " . World wars before the 20th century . Before the 20th century , there were a number of wars spanning multiple continents , including : Before the late 19th century , the concept of a world war would be the result of military action caused by quarrels between European powers which took place in fairly limited , though sometimes far - flung , theaters of conflict . World wars of the 20th century . The World Wars of the 20th century took place on almost every populated continent on Earth . Many of the states who fought in the First World War also fought in the Second , although not always on the same sides . The two World Wars of the 20th century caused unprecedented casualties and destruction across the theaters of conflict , although there are at least three wars before the 20th century with as many or more casualties than the First World War . The numbers killed in both wars combined are estimated at between 60 and 100 million people . Civilians suffered as badly as or worse than soldiers , and the distinction between military combatants and non - combatant civilians was often overlooked or ignored . Both world wars saw war crime s . Nazi Germany was responsible for multiple genocides during the Second World War , most notably the Holocaust . Both the Soviet Union and United States deported and interned minority groups within their own borders , and largely due to this conflict later many ethnic Germans were expelled in much of Eastern Europe . The Ottoman Empire is responsible for the death of over one million Armenians . Advances in technology were responsible for a large amount of casualties . The First World War saw major use of chemical weapons . The Second World War was also the first conflict in which nuclear weapons were used , devastating the Japan ese cities of Hiroshima and Nagasaki . The outcome of the World Wars had a profound effect on the course of world history . The old European empires collapsed or were dismantled as a direct result of the wars ' crushing costs and in some cases the defeat of imperial powers . The United States was firmly established as the dominant global power , along with its ideological foe , the Soviet Union , in close competition . These two superpowers exerted political influence over most of the world ' s other states for decades after the end of the Second World War ( ending in the late 1980s in the Soviet Union ) . The modern international security , economic and diplomatic system was created in the aftermath of the wars . Institutions such the United Nations were established to collectivise international affairs , with the explicit goal of preventing another outbreak of general war . The wars also greatly changed the course of daily life . Technologies developed during wartime had a profound effect on peacetime life as well — for instance , jet aircraft , penicillin , nuclear energy , and electronic computers . Since the atomic bombings of Hiroshima and Nagasaki during the Second World War , there has been a widespread and prolonged fear of a Third World War between nuclear - armed powers . Later world wars . Various former government officials , politicians and authors have attempted to apply the labels of WW III , WW IV , and WW V to various military engagements and diplomatic stand - offs since the close of WWII , such as the Cold War or the War on Terror . Among these are former American and French government officials James Woolsey and Alexandre de Marenches , author Eliot Cohen and zapatist leader Subcomandante Marcos . Despite their efforts , none of these wars are commonly deemed world wars . World War III is generally considered a hypothetical successor to World War II and is often suggested to be nuclear , devastating in nature and likely much more violent than both WW I and WW II . This war is anticipated and planned for by military and civil authorities , and explored in fiction in many countries . Concepts range from purely conventional scenarios or a limited use of nuclear weapons to the destruction of the planet . World War IV is sometimes mentioned as a hypothetical successor to World War III or as a plot element in books , movies or video games .