The missionary work in the West Indies had been hugely controversial in Europe, with many accusing Zinzendorf of simply sending young missionaries off to die. Zinzendorf decided to place himself on the line, and in 1739 left Europe to visit the mission work on St. Thomas. Convinced that he himself might not come back, he preached his "last sermon" and left his will with his wife.[4] The visit was a huge success, however, and enabled him to free some of the missionaries who had been illegally jailed. However, the missionaries' mistreatment by the plantation managers established their credibility with the slaves, and after Zinzendorf's visit the mission work was much more successful.