ground attack vs onslaught

ground attack and onslaught both are nouns.

Word	Noun	Adjective	Verb	Adverb
ground attack	Yes	No	No	No
onslaught	Yes	No	No	No

As nouns, onslaught is a hypernym of ground attack; that is, onslaught is a word with a broader meaning than ground attack:

Other hypernyms of ground attack include attack, onrush, onset.

ground attack (noun)	onslaught (noun)
an attack by ground troops	(military) an offensive against an enemy (using weapons)
	the rapid and continuous delivery of linguistic communication (spoken or written)
	a sudden and severe onset of trouble