Final answer:
Alfonso I was the king of Kongo who unsuccessfully attempted to protect his subjects from being captured and sold into slavery by appealing to the king of Portugal.
Step-by-step explanation:
Alfonso I was the king of the African state of Kongo. In an effort to stave off the capture and sale of his subjects on the slave markets, he made a poignant appeal to the king of Portugal. Despite his efforts, Alfonso I was unable to prevent Portuguese slave traders from exploiting his kingdom, and the Portuguese continued to take people from Kongo as slaves to work on sugar plantations in Brazil. Alfonso I's correspondence with João III of Portugal reflects his struggle to preserve his kingdom's integrity and the well-being of his people.