Final answer:
Missionaries were driven by their religious "calling" to spread Christianity, improve lives through education and medicine, and fulfill expansionist aims related to imperialism.
Step-by-step explanation:
Many early missionaries were motivated to endure the hardships of missionary work because of their belief that they were doing God's work and fulfilling their "calling". This included the desire to spread Protestant Christianity and its values to new regions, thus improving the lives of native populations through Christianity, education, medicine, and the introduction of modernization. Missionary societies, such as the American Board of Commissioners for Foreign Missions, conflated Christian ethics with American virtues, passionately spreading both domestically and abroad. Adherence to one's religious calling was not only seen as a path to a pious life but also integral to humanitarian work and cultural assimilation. Deeply intertwined with imperialism, missionaries across Catholic and Protestant denominations sought to convert and civilize people in accordance with their religious doctrines and the expansionist aims of their home countries.