blitzkrieg vs onset

blitzkrieg and onset both are nouns.

Word	Noun	Adjective	Verb	Adverb
blitzkrieg	Yes	No	Yes	No
onset	Yes	No	No	No

As nouns, onset is a hypernym of blitzkrieg; that is, onset is a word with a broader meaning than blitzkrieg:

blitzkrieg: a swift and violent military offensive with intensive aerial bombardment
onset: (military) an offensive against an enemy (using weapons)

Other hypernyms of blitzkrieg include attack, onrush, onslaught.

blitzkrieg (noun)	onset (noun)
a swift and violent military offensive with intensive aerial bombardment	(military) an offensive against an enemy (using weapons)
	the beginning or early stages

blitzkrieg (verb)	onset (verb)
fight a quick and surprising war