All attacks, including those of the enemy, are decided the turn before they happen. You dodge an attack by moving out of the way after an enemy has attacked you. For example, if you and a dragon are in a corner: #...
#d..
#@..
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On your turn, you attack north. The dragon is targeted by you since its in the square you are attacking.
On the dragon's turn, it moves northeast.
On your next turn, the attack happens, but the dragon isn't there any more so the attack is a miss.
Now the dragon has a turn to act again.
This means that you can only hit enemies if they are standing still or if you attack the tile they will be in next turn.