encirclement vs siege

encirclement and siege both are nouns.

Word	Noun	Adjective	Verb	Adverb
encirclement	Yes	No	No	No
siege	Yes	No	No	No

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

encirclement: a war measure that isolates some area of importance to the enemy
siege: the action of an armed force that surrounds a fortified place and isolates it while continuing to attack

Other hyponyms of encirclement include naval blockade, beleaguering, besieging, military blockade.

encirclement (noun)	siege (noun)
a war measure that isolates some area of importance to the enemy	the action of an armed force that surrounds a fortified place and isolates it while continuing to attack