Before he dies, Bolesław Krzywousty divides the country, in a limited sense, among four of his sons.

He makes complex arrangements intended to prevent fratricidal warfare and preserve the Polish state's formal unity, but after Bolesław's death the plan's implementation fails, ushering in a long period of fragmentation.

For nearly two centuries the Piasts will spar with each other, the clergy, and the nobility for the control over the divided kingdom.

The stability of the system is supposedly assured by the institution of the senior or high duke of Poland, based in Kraków and assigned to the special Seniorate Province that is not to be subdivided.

Following his concept of seniorate, Bolesław divides the country into five principalities: Silesia, Greater Poland, Masovia, Sandomierz and Kraków.

The first four provinces are given to his four sons, who became independent rulers.

The fifth province, the Seniorate Province of Kraków, is to be added to the senior among the Princes who, as the Grand Duke of Kraków, is the representative of the whole of Poland.

This principle breaks down already within the generation of Bolesław III's sons, when Władysław II the Exile, Boleslaw IV the Curly, Mieszko III the Old and Casimir II the Just fight for power and territory in Poland, and in particular over the Kraków throne.

The external borders left by Bolesław III at his death closely resemble the borders left by Mieszko I; this original early Piast monarchy configuration does not survive the fragmentation period.