First war against Swietopelk II

On 15 June 1236, Swietopelk had announced to his brothers, that he had designated his oldest son, Mestwin II, as his successor, as the duke of Pomerelia. It was against the agnatic seniority law, which stated that the eldest brother should be the successor.[1] At the time, Sambor II, with the help of the Teutonic Order, had started fortifying in the settlement of Gorzędziej. In the autumn of the same year, Swietopelk had attacked it, defeating Sambor's forces, and conquering the Duchy of Lubiszewo. After the fight, he had spared the life of his brother Sambor, exiling him from the country.[2] Additionally, Swietopelk II had formed an alliance with Sambians, Natangians and Warmians.[3]

Following that, Sambor II had aligned with the forces from Mecklenburg. Around 1237, Mecklenburgian fleet had begun fighting with Gdańsk forces alongside the coasts of Baltic Sea, later on, entering the Vistula river. In 1237 or at the beginning of 1238, Ratibor, had fortified Białogarda, and, being aided with troops of Kuyavian bishop, had attacked the Schlawe and Stolp Land, which he had subsequently conquered and plundered. At the same time Sambor II had captured the settlement of Słońca.[2] On 1 March 1238, Sambor II, together with Mecklenburgian troops, had traveled to Białogarda, in order to pursue Ratibor, to unite in the war against Swietopelk II. Soon after, Swietopelk II had defeated Sambor in the battle of Słońca, capturing the brother and keeping him captive in the settlement until around 1239. Then, he had attacked Białogarda, destroying the army of Ratibor, conquering his duchy, and burning its capital subsequently. Ratibor was also exiled to Kuyavia until 1239.[2]

Soon after it, Duchy of Kuyavia, led by Casimir I, had attacked the Duchy of Gdańsk, conquering the Bydgoszcz Castellany.[1][4][5] On 11 June 1238, Swietopelk had signed an agreement with the Teutonic Order, according to which, he wouldn't enter alliances with Prussian tribes.[1] In August 1238, Swietopelk had organized the raid on the Duchy of Kuyavia, aimed against duke Casimir I and bishop Michał, as the response to the previous attack. During the attack, his army had destroyed around 23 villages and the properties of bishops and monasteries, as well as devastated the town of Inowrocław, and had stolen a massive amount of farm animals. Following the attack, Swietopelk got excommunicated from the Catholic Church.[4][6][7] On 30 November 1238, Swietopek was put on the trial by Polish episcopal conference, against bishops of Kuyavia and Płock, Strzelno monistary and Gdańsk Dominicans, all of whom were victims of his raid. By the trial verdict, he had to financially and materrially recompensate victims, in order to end his excommunication. He never managed to fulfil it.[8] In 1239, around the Easter, Swietopelk, had realested Sambor II, and allowed Ratibor to come back from his exile, giving them both their duchies back. In return, both brothers had to pledge their allegiance to Gdańsk.[9]

• Battle of Słońca

• Second war against Swietopelk II
• Civil war in Pomerelia