Refers to a global-scale war, especially World War I or World War II. Often used in historical or political contexts.
World War I began in 1914.
世界大戦の歴史を学ぶことは重要だ。
It is important to learn the history of world wars.
World War II ended in 1945.
If it turned into a nuclear war, a new world war might break out.
That country took part in World War I.