The basic tools used by the Spanish for territorial settlement were three: missions, presidios and pueblos. The strategic combination of these allowed for the control of large, sparsely settled extents of territory. In regions such as the present-day United States, with thriving, diverse native cultures and little incentive for the introduction of settlers, missions, managed by religious congregations – initially Dominicans and Jesuits; later Franciscans – played a key role: they carried out the religious conversion of the natives and their assimilation into Spanish culture. At the same time, since they were under the supervision of religious authorities, they coud protect them to some degree from the potential abuses of civilian and military settlers.