guard ship vs combat ship

guard ship and combat ship both are nouns.

Word	Noun	Adjective	Verb	Adverb
guard ship	Yes	No	No	No
combat ship	Yes	No	No	No

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

guard ship: a warship (at anchor or under way) required to maintain a higher degree of readiness than others in its squadron
combat ship: a government ship that is available for waging war

Other hypernyms of guard ship include war vessel, warship.

guard ship (noun)	combat ship (noun)
a warship (at anchor or under way) required to maintain a higher degree of readiness than others in its squadron	a government ship that is available for waging war