<P> A world war , as it is commonly understood , is a large - scale war involving many of the countries of the world or many of the most powerful and populous ones . World wars span multiple countries on multiple continents , with battles fought in many theaters . While a variety of global conflicts have been subjectively deemed `` world wars '' , such as the Cold War and the War on Terror , the term is widely and generally accepted only as it is retrospectively applied to two major international conflicts that occurred during the 20th century : World War I ( 1914 -- 1918 ) and World War II ( 1939 -- 1945 ) . </P>
<P> A world war , as it is commonly understood , is a large - scale war involving many of the countries of the world or many of the most powerful and populous ones . World wars span multiple countries on multiple continents , with battles fought in many theaters . While a variety of global conflicts have been subjectively deemed `` world wars '' , such as the Cold War and the War on Terror , the term is widely and generally accepted only as it is retrospectively applied to two major international conflicts that occurred during the 20th century : World War I ( 1914 -- 1918 ) and World War II ( 1939 -- 1945 ) . </P>
when did world war 2 become a world war
when did world war 2 become a world war
1939
1939