pomerania was first conquered by the polish duke mieszko i in the second half of the 10th century. pagan uprisings in 1005 and 1038 resulted in independence for western pomerania and pomerelia, respectively. regained by poland in 1116/1121, the polish could not hold the pomeranian duchy longer than 1135, whereas pomerelia after the 1138 partition of poland among the sons of boleslaus wrymouth became a part of the polish seniorat, which was declared fief of the holy roman empire in 1156.