underling vs foot soldier

underling and foot soldier both are nouns.

Word	Noun	Adjective	Verb	Adverb
underling	Yes	No	No	No
foot soldier	Yes	No	No	No

As nouns, underling and foot soldier are synonyms defined as:

underling and foot soldier: an assistant subject to the authority or control of another

Other synonyms of underling include subordinate, subsidiary.

underling (noun)	foot soldier (noun)
an assistant subject to the authority or control of another	fights on foot with small arms
	an assistant subject to the authority or control of another