world war 
noun
A war involving many large nations in all different parts of the world. The name is commonly given to the wars of 1914–18 and 1939–45, although only the second of these was truly global. See First World War, Second World War.As is well known, Turing spent the second world war breaking German military codes....
- He was killed in the second world war near Dunkirk when his battalion was overrun.
- Like the First World War, each world war destroyed what went before, the values, the way of life.