John Gill Commentary 2 Chronicles 14:10

"Then Asa went out to meet him, and they set the battle in array in the valley of Zephathah at Mareshah." — 2 Chronicles 14:10 (ASV)

Then Asa went out against him
Notwithstanding he brought so great an army with him:

and they set the battle in array in the valley of Zephathah at
Mareshah ;
where the Ethiopians were; he did not stay till they got further into his country, but marched against them when on the frontiers of it, and chose the valley to pitch in, as being more to the advantage of his smaller army; see (Judges 1:17) .