military unit vs military group

military unit and military group both are nouns.

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

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

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

Other synonyms of military unit include force, military force.

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