hostilities vs armed combat

hostilities and armed combat both are nouns.

Word	Noun	Adjective	Verb	Adverb
hostilities	Yes	No	No	No
armed combat	Yes	No	No	No

As nouns, armed combat is a hypernym of hostilities; that is, armed combat is a word with a broader meaning than hostilities:

Other hypernyms of hostilities include combat.

hostilities (noun)	armed combat (noun)
fighting; acts of overt warfare	an engagement fought between two military forces