military force vs military group

military force and military group both are nouns.

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

As nouns, military force and military group are synonyms defined as:

military force and military group: a unit that is part of some military service

Other synonyms of military force include force, military unit.

military force (noun)	military group (noun)
a unit that is part of some military service	a unit that is part of some military service