enemy vs besieger

enemy and besieger both are nouns.

Word	Noun	Adjective	Verb	Adverb
enemy	Yes	No	No	No
besieger	Yes	No	No	No

As nouns, besieger is a hyponym of enemy; that is, besieger is a word with a more specific, narrower meaning than enemy:

enemy: an armed adversary (especially a member of an opposing military force)
besieger: an enemy who lays siege to your position

enemy (noun)	besieger (noun)
an opposing military force	an enemy who lays siege to your position
any hostile group of people	an energetic petitioner
an armed adversary (especially a member of an opposing military force)
a personal enemy