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.
Ground which can be freely traversed by both sides is called accessible.
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.
Ground which can be abandoned but is hard to re-occupy is called entangling.
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.
–Sun Tzu, The Art of War, Chapter X: Terrain, [1-5].
Every set of wargame rules has a section covering terrain, where you have a list of each type of terrain in and their effects on your troops. Usually this sections ends with a sentence like: “Since these rules can’t cover all of the types of terrain on the tabletop, player should use their common sense and judgement if piece of terrain comes into question.”
I’m not a fan of surprises, so I insist on going over the rules for each terrain type on the tabletop.
Flat, featureless, terrain like a field is easy to determine. It’s accessible ground with no effect on movement or cover.
Hills are a different story. In some games (or house rules), hills are more like a gentle rise and confer no penalties of benefits to movement or combat (accessible terrain). Others rules hills are consider steep, and do affect movement and combat (entangling terrain).
Sometimes the kind of troops you command determine the effect of terrain. For example, woods might be entangling terrain for regular line troops, but accessible for skirmishers.
What about low walls? Ruins? Rivers?
If you’re unclear about anything, ask questions. Clarify.
Know the rules, no surprises.
Next on The Art of Wargaming:
When The Art of Wargaming Makes the Game Boring?