under attack vs under fire

under attack and under fire both are adjectives.

Word	Noun	Adjective	Verb	Adverb
under attack	No	Yes	No	No
under fire	No	Yes	No	No

As adjectives, under attack and under fire are synonyms defined as:

under attack (adjective)	under fire (adjective)
subjected to enemy attack or censure	subjected to enemy attack or censure