On November 24, 1227, the High Duke of Poland, Leszek the White, was assassinated in an ambush on a council of Polish Dukes held in the city of Gąsawa, an event which later became known as the Gąsawa massacre.
Since Mieszko I first unified the Polish lands at the end of the 10th century, laying the basis for the development of a Polish state and integrating Poland into the prevailing European culture, Poles had been ruled by the dukes of the so-called Piast dynasty, who regarded themselves as descendants of the semi-legendary Piast the Wheelwright (Piast Kołodziej).
But the 12th century brought fundamental changes to the structure of Polish society and its political system. Upon the death of Duke Bolesław III Wrymouth in 1138, Poland was divided among his sons. The resulting internal division eroded the initial Piast monarchical structure and Poland entered a period of feudal fragmentation which lasted about 200 years.
Bolesław divided the country into five principalities: Silesia, Greater Poland, Masovia, Sandomierz and Kraków. While the first four provinces were given to his four sons, who became independent rulers, the fifth province, the Seniorate Province of Kraków, was to be added to the senior among the princes who, as High Duke, would rule over the whole of Poland.
But this principle, aimed at preserving the Polish state’s formal unity, broke down within the generation of Bolesław III’s sons, when Władysław the Exile, Bolesław the Curly, Mieszko the Old and Casimir the Just began fighting for power and territory, and particularly over the throne of Kraków, regardless of actual seniority.
The struggle for succession continued into the 13th century with Bolesław’s grandsons and by 1212, the young Leszek, son of Casimir, was invited by the Kraków nobility to assume the title of High Duke, after deposing in turn his cousins Władysław “Spindleshanks” and Mieszko “Tanglefoot”.
In addition to having to quell constant internal conflicts, the new High Duke’s prerogatives also included stabilizing Poland’s external borders and controlling the Pomeranian vassals, particularly Eastern Pomerania’s newly appointed steward, Świętopełk II, who hoped to exploit Poland’s fragmentation to gain independence from Piast overlordship.
To discuss the dangerous independentist behavior of the Pomerenian Duke, a meeting of Polish Dukes was organized in the district of Gąsawa on the border of Kujawy and Greater Poland in November 1227. It was attended by Leszek, his brother Konrad of Masovia and his Silesian ally Henry the Bearded.
But in the early morning of November 24, the princes were ambushed while bathing in preparation for retiring for the night. Henry was seriously wounded and Leszek managed to escape half-naked on his horse to the nearby village of Marcinkowo… but the assassins caught up to him and killed him.
While the Gąsawa massacre served Świętopełk’s interests, several historians have also suggested that the Pomerenian Duke might have conspired with Duke Władysław Odonic, who was involved in a long-running conflict over control of Greater Poland and with whom Świętopełk had forged an alliance shortly before the attack. But whatever the exact circumstances of, or the responsibility for, the event, it is generally accepted that Gąsawa massacre contributed to the deepening of the feudal fragmentation of Poland.
Świętopełk II declared himself independent from Polish overlordship and, with the authority of the High Duke now severely undermined, the so-called Seniorate Province of Kraków essentially became just another feudal area to be fought over. Poland, as a unified political entity, would not be re-established until the 14th century and the reign of Casimir III the Great, the last ruler of the Piast dynasty.
Casimir the Great was indeed succeeded by his nephew, Louis I of Hungary of the Angevin dynasty, whose daughter Jadwiga later married Grand Duke Jogaila of Lithuania in 1386, creating a dynastic union between Poland and Lithuania and binding the two countries together for the next four centuries…
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