field-grade officer vs military

field-grade officer and military both are nouns.

Word	Noun	Adjective	Verb	Adverb
field-grade officer	Yes	No	No	No
military	Yes	Yes	No	No

field-grade officer (noun)	military (noun)
an officer holding the rank of major or lieutenant colonel or colonel	the military forces of a nation

field-grade officer (adjective)	military (adjective)
	associated with or performed by members of the armed services as contrasted with civilians
	characteristic of or associated with soldiers or the military
	of or relating to the study of the principles of warfare