Petersburg Campaign vs besieging

Petersburg Campaign and besieging both are nouns.

Word	Noun	Adjective	Verb	Adverb
Petersburg Campaign	Yes	No	No	No
besieging	Yes	No	No	No

Petersburg Campaign (noun)	besieging (noun)
the final campaign of the American Civil War (1864-65); Union forces under Grant besieged and finally defeated Confederate forces under Lee	the action of an armed force that surrounds a fortified place and isolates it while continuing to attack