So the army went out into the field against Israel, and the battle was fought in the forest of Ephraim.
Which way David raised an army here, and what reinforcements were sent him, we are not told; many, it is likely, from all the coasts of Israel, at least from the neighbouring tribes, came in to his assistance, so that, by degrees, he was able to make head against Absalom, as Ahithophel foresaw. Now here we have, I. His army numbered and marshalled, Sa2 18:1, Sa2 18:2.
Commenting on 2 Samuel 18:1-8
So the people went out into the field against Israel,.... Josephus (e) calls it a great field, with a wood behind it: and the battle was in the wood of Ephraim; or near it (f) rather; not in a wood in the tribe of Ephraim, which lay on this side Jordan; whereas this battle was fought on the other side Jordan, in the land of...
wood of Ephraim--This wood, of course, was on the east of Jordan. Its name was derived, according to some, from the slaughter of the Ephraimites by Jephthah--according to others, from the connection of blood with the trans-jordanic Manasseh.