war god vs god of war

war god and god of war both are nouns.

Word	Noun	Adjective	Verb	Adverb
war god	Yes	No	No	No
god of war	Yes	No	No	No

As nouns, war god and god of war are synonyms defined as:

war god (noun)	god of war (noun)
a god worshipped as giving victory in war	a god worshipped as giving victory in war