This unfortunate desert land is an example of what the scholars of our world call a "hydraulic despotism."
Like Egypt of old, it is a highly developed civilisation in the midst of a harsh desert. As such it relies on the constant flow of water. The flow of water, in turn, is maintained by an intricate system of dams, pumps, and canals.
Thus the farmer who defies the government may be destroyed with the turn of a wheel. The runaway has nothing to run to but thirst and death. And, in a land where the only liveable land is near a well-maintained canal, where is there to hide?
The head of the civil service has therefore, over the centuries, become also the monarch, high priest, and finally a living god.
The army are slaves, bought as infants from Karsh, and raised with no loyalty but to the state. This, at least, is the theory, but the ruler has at times been the slave of their slaves, and it may be that some have gone from general to god. It is impossible to say how many dynasties have been founded in this way, or by the garotte or blade wielded by concubine or servant. The histories, little more than myth, speak only of an unbroken line of rulers, serene and unchanging over a serene and unchanging land.
The common folk (all who are not royalty, their servants, or canal-priests) are subject to conscription, not military but of their labour. Most projects relate either to the flow of water, or to the empire's increasingly monumental religion.
All this being said, some more free-spirited souls have managed to survive in the desert, and there are bands of nomads who roam the fringes of the empire, threatening it not at all in concrete reality, but a great shadow in the minds of the rulers.