47. How a new dynasty originates.
It should be known that when the ruling dynasty starts on the road to senility and destruction, the rise and beginning of the new dynasty takes place in two ways:
(The one way is) for provincial governors in the dynasty to gain control over remote regions when (the dynasty) loses its influence there. Each one of them founds a new dynasty for his people and a realm to be perpetuated in his family. His children or clients inherit it from him. Gradually, they have a flourishing realm. They often compete bitterly with each other and aspire to gain sole possession of it. The one who is stronger than his rival will gain the upper hand and take away what the other had.
This happened in the 'Abbasid dynasty when it started on the road to senility and its shadow receded from the remote regions. The Samanids gained control over Transoxania, the Hamdinids over Mosul and Syria, and the Tulunids over Egypt. The same thing happened in the Umayyad dynasty in Spain. Their realm was divided among the reyes de taifas who had been their provincial governors. It was divided into several dynasties with several rulers, who passed their realms on after their death to their relatives or clients. This way of forming a new dynasty avoids the possibility of war between the (new rulers) and the ruling dynasty. (These new rulers) are already firmly established in their leadership and do not want to gain domination over the ruling dynasty. The latter is affected by senility, and its shadow recedes from the remote regions of the realm and can no (longer) reach them.
The other way is for some rebel from among the neighboring nations and tribes to revolt against the dynasty. He either makes propaganda for some particular cause to which he intends to win the people, as we have indicated,728 or he possesses great power and a great group feeling among his people. His power is already flourishing among them, and now he aspires with the help of (his people) to gain royal authority. (His people) are convinced that they will obtain it, because they feel that they are superior to the ruling dynasty, which is affected by senility. Thus, to (the rebel) and his people, it is a fact that they will gain domination over it. They constantly attack it, until they defeat it and inherit its power.
This was the case with the Saljugs in relation to the descendants of Sebuktigin, and with the Merinids in the Maghrib in relation to the Almohads.
"God has the power to execute His commands." 729