besieger vs foeman

besieger and foeman both are nouns.

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

As nouns, foeman is a hypernym of besieger; that is, foeman is a word with a broader meaning than besieger:

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

Other hypernyms of besieger include enemy, foe, opposition.

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