Accordingly, in June 1654 he set sail for Lisbon to plead the cause of the Indians, and in April 1655 he obtained from the king a series of decrees which placed the missions under the Society of Jesus, with himself as their superior, and prohibited the enslavement of the natives, except in certain specified cases. Returning with this charter of freedom, he organized the missions over a territory having a coast-line of 400 leagues, and a population of 200,000 souls, and in the next six years (1655–61) the indefatigable missionary set the crown on his work. After a time, however, the colonists, attributing the shortage of slaves and the consequent diminution in their profits to the Jesuits, began actively to oppose Vieira, and they were joined by members of the secular clergy and the other Orders who were jealous of the monopoly enjoyed by the company in the government of the Indians.