bridgehead

bridgehead
    n 1: an area in hostile territory that has been captured and is
         held awaiting further troops and supplies; "an attempt to
         secure a bridgehead behind enemy lines"; "the only foothold
         left for British troops in Europe was Gibraltar" [syn:
         {bridgehead}, {foothold}]
    2: a defensive post at the end of a bridge nearest to the enemy
    

Bridgehead \Bridge"head`\, n.
   A fortification commanding the extremity of a bridge nearest
   the enemy, to insure the preservation and usefulness of the
   bridge, and prevent the enemy from crossing; a
   t[^e]te-de-pont.
   [1913 Webster]
    

53 Moby Thesaurus words for "bridgehead":
      acropolis, advance guard, airhead, avant-garde, bastion,
      battle line, beachhead, blockhouse, bunker, castle, citadel,
      donjon, farthest outpost, fasthold, fastness, first line,
      forefront, fort, fortress, front, front line, front rank,
      front-runner, garrison, garrison house, hold, keep, line, martello,
      martello tower, mote, motte, outguard, outpost, peel, peel tower,
      pillbox, pioneer, point, post, precursor, railhead, rath, safehold,
      scout, spearhead, strong point, stronghold, tower,
      tower of strength, van, vanguard, ward