Swietopelk II, Duke of Pomerania
Swietopelk II, also Zwantepolc II or Swantopolk II, (1190/1200 – 11 January 1266), sometimes known as the Great (Polish: Świętopełk II Wielki; Kashubian: Swiãtopôłk II Wiôldżi), was Duke of Pomerelia-Gdańsk from 1215 until his death. He was a son of Mestwin I and the first member of the Samborides to style himself dux (from 1227 onwards).
The duke is known under many spellings (Swantepolk, Swantipolk, Svatopluk, Swietopelk, Swatopolk, Sviatopolk, Światopełek, Świętopełk, Swiãtopôłk), of which Domin(us) Zwantepolc(us) D(ux) Danceke and Svantopelc Ducis Pomeranie were used on seals.
In 1216 or 1217 Swietopelk was made a steward over Pomerelia or Eastern Pomerania by Leszek the White of Kraków. He was responsible for Gdańsk castle territory, the largest of the four portions of Pomerelia. In 1218, Swietopelk took advantage a revolt of local knights against Danish rule to acquire Słupsk and Sławno. After his brother Warcislaw died without heirs, Swietopelk took over his Lubiszewo Tczewskie.
Swietopelk's brothers Sambor and Racibor were still young, so he acted as their guardian. As they came of age, the brothers received their share of inheritance: Sambor received Lubiszewo Tczewskie and Racibor received Białogard.
Swietopelk, who had exploited Piast Poland's fragmentation to gain independence, promised Władysław Odonic the throne of Kraków and Silesia in exchange for his support in the ousting of Leszek and Henry I the Bearded of Lower Silesia. On 23 November 1227, on the occasion of an assembly of Piast dukes in Gąsawa, Leszek was killed in an ambush set by Swietopelk II and perhaps Władysław, while Henry was severely wounded.
In 1238 Swietopelk conquered the Duchy of Sławno, whose territories connected Pomerania to Gdańsk, Nakło, and Bydgoszcz. This guaranteed war with Kujavia. The brothers, over whom Swantopolk 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 Racibor 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 Swantopolk. This resulted in an alliance with the heathen Prussians. Swantopolk played a key role in the First Prussian Uprising, which started in 1242 after the Teutonic Knights lost the Battle of the Ice.
The alliance between the pagan Prussians and the Christian Swietopelk against a religious order supported by the pope was unexpected. Swietopelk 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. Swietopelk 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).
- 1217/1218 Eufrozyna, daughter of Odon, duke of Greater Poland (she was his sister´s sister in law and half-cousin through Miezsko III)
- before 1252 (?) Ermenegarda of Mecklenburg
- Mestwin II, duke of Świecie (Schwetz) and later Gdańsk (Danzig)
- Wratislaw II, duke of Gdańsk
- Eufemia, married to Jaromar II, prince of Rugia
- Zwinisława, married to Dobiesław, son of Sad, lord of Tega and Otorów near Wyszogród
- unknown daughter, married to a Count of Kevenberg
- F. Cenôwa: Trze rosprave: przez Stanjisława ; wóros Kile słóv wó Kaszebach e jich zemji przez Wójkasena, Kraków: Nak. Ksi. i Czcion. pod Sową, 1850, p. 31 
- Loew PO: Danzig. Biographie einer Stadt, Munich 2011, p. 32: "Sambor [...] styled himself 'princeps Pomoranorum,' [...], but not 'dux,' which was the privilege of the Piasts." p. 33: "After Sambor's death [...] his brother Mestwin [...] strove after gaining ever greater independence from Poland. He confidently styled himself 'princeps in Danzk' and expanded southwards. His oldest son Swantopolk (Swietopelk), ruling from 1217 onwards, exploited Poland's fragmentation to acquire independence for his realm; already since 1227 he styled himself 'dux,' 'Duke of Pomerelia.'"
- pl:Marian Gumowski: Handbuch der polnischen Siegelkunde, 1966 
- Edmund Cieślak; Historia Gdańska, 1978
- Edward Rymar, Rodowód książąt pomorskich (Genealogy of Dukes of Pomerania), Książnica Pomorska, 2005, pg. 240
- Christiansen, Eric (1997). The Northern Crusades (2nd ed.). Penguin Books. pp. 105–108. ISBN 0-14-026653-4.
- Urban, William (2000). The Prussian Crusade (2nd ed.). Chicago, Illinois: Lithuanian Research and Studies Center. pp. 185–189. ISBN 0-929700-28-7.
- Brown Mason, John (1946). The Danzig Dilemma: a Study in Peacemaking by Compromise. Oxford University Press.
- (German) Hirsch, Theodor; Max Töppen, Ernst Strehlke (1861). Scriptores Rerum Prussicarum: Die Geschichtsquellen der preussischen Vorzeit. S. Hirzel. pp. 797, 807.