"Bats are frightfully fast and deadly in swarms, but are easily wiped out by splash damage."
Bats are periodically summoned by the Night Witch to aid her in battle.
These are just like Skeletons, however they fly. This allows them to evade ground defenses.
Bats don't deal much damage, but they have power in number.
Bats have no preferred target when attacking; they will simply attack the closest building to them. However, once they become aware of enemy Guard Post troops (either by being attacked themselves or being near another friendly troop under attack), they will leave their previously targeted building and engage the enemy troops instead. Once all of the nearby enemy troops are defeated, they will proceed to attack the nearest building from their current location.
Try to take out the Crusher(s) with the bats and the Night Witch so you can swarm the village with many ground units.
The bats can help the Night Witch take out many defensive buildings before she gets targeted.
Try to avoid Air Bombs and the Roaster as they are splash damage air targeting defenses.