1. [n]  an armed adversary (especially a member of an opposing military force); "a soldier must be prepared to kill his enemies"
2. [n]  a personal enemy; "they had been political foes for years"

Foe
Daniel Foe, a famous writer, is the confidant of a castaway named Susan Barton who, when she was rescued from a remote island by a passing ship, was accompanied by Robinson Crusoe`s servant, Friday--a silent man who has had his tongue cut out, and who seems to have forgotten his old life.

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1. \Foe\ (f[=o]), n. [OE. fo, fa, AS. f[=a]h hostile; prob.
   akin to E. fiend. [root]81. See {Fiend}, and cf. {Feud} a
   quarrel.]
   1. One who entertains personal enmity, hatred, grudge, or
      malice, against another; an enemy.
            A man's foes shall be they of his own household.
                                                  --Matt. x. 36
   2. An enemy in war; a hostile army.
   3. One who opposes on principle; an opponent; an adversary;
      an ill-wisher; as, a foe to religion.
            A foe to received doctrines.          --I. Watts
   

2. \Foe\, v. t.
   To treat as an enemy. [Obs.] --Spenser.