The Collaborative International Dictionary of English v.0.48:

Belligerence \Bel*lig"er*ence\, Belligerency \Bel*lig"er*en*cy\,
   n.
   The quality of being belligerent.
   [1913 Webster]

   2. the act or state of being engaged in war or a warlike
      conflict; warfare.

   Syn: hostilities.
        [WordNet 1.5]

   3. an aggressively hostile or warlike attitude or nature; a
      readiness to fight or offend, with little or no
      provocation.
      [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

belligerence
    n 1: hostile or warlike attitude or nature [syn: belligerence,
         belligerency]
    2: a natural disposition to be hostile [syn: aggressiveness,
       belligerence, pugnacity]