<P> Since the atomic bombings of Hiroshima and Nagasaki during the Second World War, there has been a widespread and prolonged fear of a potential Third World War between nuclear - armed powers . The Third World War is generally considered a successor to the Second World War and is often suggested to become a nuclear war, devastating in nature and likely much more violent than the First World War and the Second World War combined; in 1947, Albert Einstein commented that "I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones ." It has been anticipated and planned for by military and civil authorities and has been explored in fiction in many countries . Concepts have ranged from purely - conventional scenarios, to limited use of nuclear weapons, to the complete destruction of the planet's surface . </P> <P> Various former government officials, politicians, authors, and military leaders (including the following people: James Woolsey Alexandre de Marenches, Eliot Cohen, and Subcomandante Marcos) have attempted to apply the labels of the "Third World War" and "Fourth World War" to various past and present global wars since the closing of the Second World War, for example, the Cold War and the War on Terror, respectively . Among these are former American, French, and Mexican government officials, military leaders, politicians, and authors: Despite their efforts, none of these wars are commonly deemed world wars . </P> <P> The Second Congo War (1998--2003) involved nine nations and led to ongoing low - level warfare despite an official peace and the first democratic elections in 2006 . It has often been referred to as "Africa's World War". During the early - 21st century the Syrian Civil War and the Iraqi Civil War and their worldwide spillovers are sometimes described as proxy wars waged between the United States and Russia, which led some commentators to characterize the situation as a "proto - world war" with nearly a dozen countries embroiled in two overlapping conflicts . </P> <P> The two world wars of the 20th century had caused unprecedented casualties and destruction across the theaters of conflict . There have been several wars that occurred before the 20th century with as many or more deaths than in the First World War (16,563,868--40,000,000), including: </P>

How many countries have to be involved to be a world war