PERFORCE
perforce
(adverb) by necessity; by force of circumstance
Source: WordNet® 3.1
Etymology
Adverb
perforce (not comparable)
(archaic) By force.
Necessarily.
Verb
perforce (third-person singular simple present perforces, present participle perforcing, simple past and past participle perforced)
(obsolete) To force; to compel.
Source: Wiktionary
Per*force", adv. Etym: [F. par (L. per) + force.]
Definition: By force; of necessary; at any rate. Shak.
Per*force", v. t.
Definition: To force; to compel. [Obs.]
Source: Webster’s Unabridged Dictionary 1913 Edition