It depends how you define World The war which commenced in 1939 was only between European states while the two most industrially powerful countries on the globe USA and Soviet Union were not at war It only becomes an actual world war in 1941 It could be rationally argued that if the war had ended before 1941 before the USA and SU got involved then it would just have been called the European War or the Great Nazi War or the Anglo Franco German War or something similar It is difficult to see why a war which leaves out the two most powerful countries on Earth could in any real sense be called a world war And I am writing this as a European Still the war has to be called something and once it became a world war in 1941 then the name could retrospectively be applied to the fighting which preceded it