the leeward.
[Chang Yu, following Tu Yu, says: "When you make a fire, the enemy will
retreat away from it; if you oppose his retreat and attack him then, he
will fight desperately, which will not conduce to your success." A
rather more obvious explanation is given by Tu Mu: "If the wind is in
the east, begin burning to the east of the enemy, and follow up the
attack yourself from that side. If you start the fire on the east side,
and then attack from the west, you will suffer in the same way as your
enemy."]