2 Kings 3:21

And[R.V. Now] when all the Moabites heard By the circuitous journey which the armies had made their march would be less observed, and it would only be at the time of their appearance on the frontier that the object of their expedition would become known. But the casting off the yoke of Israel, and the freeing of their land from such a burdensome tribute made the war popular in Moab, and all were prepared to do their duty against the invaders.

come up See above on verse 7.

they gathered all thatwere able to put on armour R.V. they gathered themselves together, all &c. The verb is literally, -they called themselves together". The expression indicates the enthusiasm with which each man appealed to his neighbour. -To put on armour" is literally -to gird themselves with a girdle", for to the girdle the weapon was attached.

and stood in the border This would naturally be a height dividing their country from the land of Edom.