1 Chronicles 19:9
And the children of Ammon came out, and put the battle in array before the gate of the city: and the kings that were come were by themselves in the field. And the children of Ammon came out, and put the battle in array before the gate of the city: and the kings that were come were by themselves in the field.
The Ammonite army came out from the city and drew up in battle order directly before the city gate. The allied kings who had come to their aid did not join that line but remained apart by themselves out in the open field. The enemy was thus divided into two separate forces, one at the gate and one in the field. To meet that divided array Israel likewise divided its own army into two parts. Joab took command of the choice young men and led them against the Syrians, while Abishai took command of the remainder of the troops and led them against the Ammonites.