Question

How might understanding geography, specifically landforms and bodies of water, be useful to a general who is strategizing a battle?

Answer 1

For a general, it would be very important to know where various geographic landmarks are because it would help them maneuver their troops without running into any obstacles.

Answer 2

So the general knows where the enemies blind spots are. Moreover you can corner them. Doing so will help you win the battle. Not knowing these things results in a high chance of defeat.