The Viking Age and early Middle Ages saw the beginning of political unification in the larger territories, leading to the creation of the kingdoms of Denmark, Norway and Sweden, and the Free State of Iceland. The early political unification was the outcome of political decisions made by individuals, and of military force. The formation of the kingdoms involved the development of a more elaborate and formalised military organisation. The breaking up of the Danish North Sea empire and the consequent weakening of the Danish kingdom made it possible for Norwegian kings to establish a more permanent rule over most of their later territory. In Sweden the tendencies towards political unification came later and were weaker than in Denmark and Norway. In the process of political and social transformation Christianity and the Church were of crucial importance. Christianity and its ecclesiastical organisation were also means of enhancing the kings's power and prestige.