A high security palisade fence is formed from a plurality of vertical posts, each of which is characterized by a pair of flange sections which are joined by an intermediate flat web section having a double-walled structure. One or more cable passageways are formed in each post. Each adjacent pair of posts is interconnected by a plurality of parallel rails. Each rail is formed with an internal tray, within which a strengthening cable may extend. Vertical pickets are attached to the rails. The pickets are preferably characterized by a W-shaped profile, and preferably include longitudinal strengthening ribs. Each picket has a flat attachment surface in which a plurality of subsurface recesses are formed.