‘The burden of Moab.
For in a night Ar of Moab is laid waste,
It is brought to nought.
For in a night Kir of Moab is laid waste.
It is brought to nought.
He is gone up to Bayith, and to Dibon,
To the high places to weep.
Moab howls over Nebo,
And over Medeba.
On all their heads is baldness,
Every beard is cut off.'
In chapter 14 Isaiah ended with the approaching dust clouds of the Assyrian army, and the failing hearts of the Philistines. Now he moves on to their actual approach on one of the rebel nations, on Moab. The inevitable is described. Assyria's power is such that nothing human can stand before their armies. So effective is their siege expertise that the cities of Ar and Kir are both laid waste in a single night. Both are brought to nought.
However Kir means ‘city'. Thus the idea may be of ‘each city' rather than one particular city, that is, a number of cities. Indeed Nebo and Medeba have fallen. The cities are mentioned in the main from south to north. ‘He' is probably Moab. So the idea is that the Moabites go to Bayith and Debir to weep before their gods in the high places. The whole of Moab weeps. They make themselves bald and cut off their beards, both evidences of severe mourning.