grenade thrower vs foot soldier

grenade thrower and foot soldier both are nouns.

Word	Noun	Adjective	Verb	Adverb
grenade thrower	Yes	No	No	No
foot soldier	Yes	No	No	No

As nouns, foot soldier is a hypernym of grenade thrower; that is, foot soldier is a word with a broader meaning than grenade thrower:

Other hypernyms of grenade thrower include footslogger, infantryman, marcher.

grenade thrower (noun)	foot soldier (noun)
an infantryman equipped with grenades	fights on foot with small arms
	an assistant subject to the authority or control of another