TERRAIN

 1. Sun Tzu said: We may distinguish six kinds of terrain,
  to wit: (1) Accessible ground; (2) entangling ground;
  (3) temporizing ground; (4) narrow passes; (5) precipitous
  heights; (6) positions at a great distance from the enemy.

 2. Ground which can be freely traversed by both sides
  is called accessible.

 3. With regard to ground of this nature, be before
  the enemy in occupying the raised and sunny spots,
  and carefully guard your line of supplies. Then you
  will be able to fight with advantage.

 4. Ground which can be abandoned but is hard
  to re-occupy is called entangling.

 5. From a position of this sort, if the enemy
  is unprepared, you may sally forth and defeat him. 
  But if the enemy is prepared for your coming, and you
  fail to defeat him, then, return being impossible,
  disaster will ensue.