The phrase "a war break out" is correct and can be used in written English.
It means that a war has started. Example: When a war broke out in Syria, millions of people were displaced.
Could a war break out between India and China — again?
"Should a war break out on the Korean Peninsula due to the U.S. imperialists, it will escalate into a nuclear war," Mr. Kim said, according to the announcer.
An independent NATO, with its own nuclear deterrent, responsible for the defense of Western Europe, willing to make the sacrifices to fight (with American help, if necessary) and win a conventional war with the Soviet Union should such a war break out - that is the NATO of the future, if NATO is to survive at all.
K. Adie (Kate), a watcher getting broadcast when a war breaks out (anag. less a war).
The history goes back 10 years, when a war broke out in the middle of Europe.
There's a war breaking out in the House Intelligence Committee over the unfolding Russia scandal.
A war broke out in 1980 after Saddam Hussein claimed the river for Iraq.
If the prototype were implemented and a war broke out in Greece, soldiers could scope out the building in advance.
"Of course, if a war breaks out in a significant way or something like that happens," he said, "then I would give you a different answer.
