Testament of Bolesław III Wrymouth

The last will and testament of the Piast duke Bolesław III Wrymouth of [Poland during the Piast dynasty|Piast dynasty|Poland], established rules for governance of the [Kingdom of Poland during the Piast dynasty|Poland (1025–1385)|Polish kingdom] by his four surviving sons after his death. By issuing it, Bolesław planned to guarantee that his heirs would not fight among themselves, and would preserve the unity of his lands under the Piast dynasty. However, soon after his death his sons fought each other, and Poland entered a period of fragmentation lasting about 200 years.

Provisions

Bolesław III issued the document around January 1115 ; it would be enacted upon his death in 1138.
Bolesław divided the country into five principalities:

the Seniorate Province, composed of western Lesser Poland, the eastern parts of Greater Poland, western Kuyavia and Wieluń Land assigned to Bolesław's eldest son and future High Duke Władysław II, as well as the lands of Łęczyca Province which were held by Bolesław's widow Salomea of Berg for life and to revert to the Seniorate Province upon her death;
the Silesian Province, comprising Silesia, also assigned to Władysław II;
the Masovian Province, composed of Masovia proper and eastern Kuyavia, assigned to Bolesław's III second son Bolesław IV the Curly;
the Greater Poland Province, composed of the remaining western parts of Greater Poland, assigned to the third son Mieszko III the Old,
the Sandomierz Province, composed of eastern Lesser Polish territories centered around the city of Sandomierz, assigned to the fourth son Henry of Sandomierz.

The youngest son Casimir II the Just was not assigned any province; it is speculated that he was born after Bolesław's death, or that he was destined for a religious career.
The senioral principle established in the testament stated that at all times the eldest member of the dynasty was to have supreme power over the rest and was also to control an indivisible "seniorate province" : a vast strip of land running north–south down the middle of Poland, with Kraków its chief city. The Senior's prerogatives also included control over the Pomeranian vassals in Pomerelia, as a fief. The Senior was tasked with defense of borders, the right to have troops in provinces of other Dukes, carrying out foreign policy, supervision over the clergy, and minting of currency.

Aftermath

The senioral principle was soon broken, with Władysław II attempting to increase his power and his younger half-brothers opposing him. After initial success, he was eventually defeated and expelled from Poland in 1146. With the help of Emperor Frederick I Barbarossa his sons managed to retain the Silesian Province in 1163, losing the Seniorate, which had passed to their uncle Bolesław IV. This led to a period of nearly 200 years of Poland's feudal fragmentation; the estrangement of the Silesian Piasts deepening after the death of Duke Henry II the Pious at the disastrous Battle of Legnica in 1241.
The Polish throne at Kraków remained contested between the descendants of Bolesław's III sons. Once Duke Władysław I the Elbow-high, a descendant of Casimir II the Just, was crowned King of Poland in 1320, he would reign on a smaller dominium, with Pomerelia lost to the State of the Teutonic Order and Silesia mostly vassalized by the Kingdom of Bohemia.