South of the Yarmuk the black basalt of the Jaulan yields to the light limestone of the west-jordan.
Its valleys in the west-jordan were the home of the agriculturist.
Like the Shephelah or lowland on the west it is a distinct physical division of the west-jordan land.
The city was the natural key to the west-jordan country and therefore its chief defence against invaders from the east.
The Ammonites, recognizing the significance of the new west-jordan power, assumed the initiative and insulted David's messengers.