So David's army marched into the field to engage Israel in the battle, which took place in the forest of Ephraim.

Joshua 17:15
Joshua answered them, "If you have so many people that the hill country of Ephraim is too small for you, go to the forest and clear for yourself an area in the land of the Perizzites and the Rephaim."

Joshua 17:18
because the hill country will be yours as well. It is a forest; clear it, and its farthest limits will be yours. Although the Canaanites have iron chariots and although they are strong, you can drive them out."

2 Samuel 17:26
So the Israelites and Absalom camped in the land of Gilead.

2 Samuel 18:7
There the people of Israel were defeated by David's servants, and the slaughter was great that day--twenty thousand men.

So the people went out into the field against Israel: and the battle was in the wood of Ephraim;