On their accession to power, the Rügen princes were forced to confirm their allegiance to the Danish king and were obliged to provide military support to the Danes.
[citation needed] Because he had no children at that time, Rügen's princely house risked becoming extinct, so in 1310 at Ribnitz he agreed to a contract of inheritance with his feudal lord, the Danish king Eric VI Menved.
At that time, Eric VI Menved was attempting to extend his power in the southern Baltic Sea region in order to reduce the influence of Hanseatic towns like Stralsund.
After the death of Eric VI Menved in 1319, the 1310 treaty lapsed and Vitslav III sought allies in the Pomeranian dukes.
In late summer of 1326, Henry took advantage of the situation and occupied the western territories on the mainland that belonged to the Principality of Rügen.
After announcing a planned kidnapping by the Baron of Schwerin, resident in Spantekow and Altwigshagen, the oldest son, Bogislaw, was again taken to Greifswald for safety.
On 27 June 1328, in the village of Brudersdorf [de] near Dargun, a peace treaty was signed between Duke Barnim III of Stettin, guardian of Vartislav IV's sons, Henry II of Mecklenburg, and John of Werle.
In return for 31,000 silver marks of Cologne weight, to be paid over the following twelve years, Mecklenburg renounced its claim on the Principality of Rügen.
Valdemar IV Atterdag, the former feudal lord, avoided making a decision, fearing that the losing party would desert him.
Because the sons of Vartislav IV of Pomerania-Wolgast could not redeem the pledged estates, but continued to claim them back, there was renewed fighting with Mecklenburg in 1351.
With the support of Barnim III of Pomerania-Stettin, an army led by Baron Klaus Hahn inflicted a devastating defeat on Mecklenburg on 25 October 1351 at the Schopendamm near Loitz.
Tribsees went to Pomerania in 1355, since it belonged to the jointure of Vitslav III's widow, Anne of Lindow-Ruppin, who had married Henry II.