bulwark vs defend

bulwark is a noun but defend is not a noun.

Word	Noun	Adjective	Verb	Adverb
bulwark	Yes	No	Yes	No
defend	No	No	Yes	No

As verbs, defend is a hypernym of bulwark; that is, defend is a word with a broader meaning than bulwark:

bulwark (noun)	defend (noun)
a protective structure of stone or concrete; extends from shore into the water to prevent a beach from washing away
an embankment built around a space for defensive purposes
a fencelike structure around a deck

bulwark (verb)	defend (verb)
defend with a bulwark	argue or speak in defense of
	state or assert
	be on the defensive; act against an attack
	protect against a challenge or attack
	protect or fight for as a champion
	fight against or resist strongly
	be the defense counsel for someone in a trial