enemy vs military group

enemy and military group both are nouns.

Word	Noun	Adjective	Verb	Adverb
enemy	Yes	No	No	No
military group	Yes	No	No	No

As nouns, military group is a hypernym of enemy; that is, military group is a word with a broader meaning than enemy:

Other hypernyms of enemy include force, military force, military unit.

enemy (noun)	military group (noun)
an opposing military force	a unit that is part of some military service
any hostile group of people
an armed adversary (especially a member of an opposing military force)
a personal enemy