Swietopelk was the son of the
Pomeranian duke
Mestwin I and his wife Swinisława. His father had ruled over
Eastern Pomerania (or Pomerania) since about 1205 by appointment of the
Polish high duke
Władysław III Spindleshanks. In 1216 or 1217, his son Świętopełk was made a
steward over Pomerelia by High Duke
Leszek I the White of
Kraków. He was responsible for the Gdańsk territory, the largest of the four portions of Pomerelia. In 1218, Swietopelk took advantage of a revolt of local knights against
Danish rule to occupy the
Lands of Schlawe and Stolp. After his brother Warcislaw died without heirs, Świętopełk took over his
Lubiszewo Tczewskie. As they came of age, the brothers received their share of inheritance: Sambor received
Lubiszewo Tczewskie and Ratibor received
Białogarda. Świętopełk, who had exploited Piast Poland's fragmentation to gain independence, In 1238, Świętopełk conquered the
Duchy of Pomerania-Schlawe, whose territories connected Pomerania to
Gdańsk,
Nakło, and
Bydgoszcz. This guaranteed war with
Kuyavia. The brothers, over whom Świętopełk was supposed to govern for twenty years, refused to support their overlord after twelve years, and the conflict escalated into a civil war. Sambor and Ratibor were driven out from their lands and sought refuge and alliance first with Piast relatives in
Greater Poland, later with the
Teutonic Knights, a
Christian military order
waging a crusade against
pagan Prussians. There were also economic tensions between the Knights and Świętopełk. This resulted in an alliance with the heathen Prussians. Świętopełk played a key role in the
First Prussian Uprising, which started in 1242. The alliance between the pagan Prussians and the Christian Świętopełk against a religious order supported by the
Pope was unexpected. Świętopełk was previously known as a supporter of the
Roman Catholic Church and Christian causes. Eventually, the uprising did not succeed and a peace treaty, mediated by a
papal legate, was signed on 24 November 1248. Świętopełk had to return lands seized from his brothers, allow Teutonic Knights to pass through his domains, stop charging tolls on ships using the
Vistula, and stop any aid to the Prussians. He kept his word and did not assist the Prussians during their
Great Uprising (1260–1274). After governing since 1220 for 46 years, Świętopełk died in 1266, with his sons
Mestwin II and
Wartislaw II inheriting his lands. == Family ==