Noun
The area in which armed conflict takes place.
(figuratively) A subject that is highly contentious; an area of conflict.
Source: en.wiktionary.orgIt is necessary to keep in mind the possibility of simultaneously conducting two, if not three, offensive operations of various fronts on a theater of war with the intention of strategically shaking the enemy's entire combat capability as extensively as possible. Semyon Timoshenko
As soon as I read that, it clicked: that's my theater of war. It was exciting to think that I could write about World War Two from a totally new place. Michael Chabon
We can guess that the unacceptable conduct of the soldiers at Abu Ghraib resulted in part from the dangerous state of affairs on the ground in a theater of war. John Yoo