2 Samuel 18:6-8 NIV

6 The army marched into the field to fight Israel, and the battle took place in the forest1 of Ephraim.

References for 2 Samuel 18:6

7 There the army of Israel was defeated by David's men, and the casualties that day were great--twenty thousand men.
8 The battle spread out over the whole countryside, and the forest claimed more lives that day than the sword.