The Danish organized a war to Christianize the formerly pagan islanders and to destroy the pagan strongholds and cult places. This action also served to have their
piracy and raids to Danish lands ended. The Danish navy, led by among other militaries, Archbishop
Absalon, conquered and destroyed the fortress of
Cape Arkona. The temple fortress of Arkona (
Jaromarsburg) had been the religious centre of the Slavic Rani. The island of Rügen was incorporated into the Danish
Archdiocese of Roskilde. The Danish set up Rügen as their vassal. Jaromar, who was not committed to hitherto pagan rulers of the island, accepted
Christianity and promised loyalty to King
Valdemar I of Denmark. Jaromar allied with the
Hvide and Galen
magnate clans, who were leaders of
Zealand and
Skåne. Jaromar had his son and heir
Wizlaw I marry a lady from these Danish magnates' families, who were influential in those parts of
Denmark that were closest to Rügen. By 1185, Jaromar I had started construction of St. Mary's Church (
Marienkirche) erected in his stronghold
Rugard (which later became the town
Bergen-auf-Rügen). In 1193, the church was completed and then consecrated as a
monastery church, making it Rügen's oldest maintained building. It is commonly believed that Jaromar was buried under the gravestone embedded in the church's outer wall. Additionally he founded the
Cistercian Eldena Abbey (
Kloster Eldena). ==Family==