Final answer:
The Portuguese Crown mandated conversion campaigns to accompany military pacification of Native Americans, later codifying the legal status of natives, which included conditions for enslavement. As native populations declined, the Portuguese turned to African slave labor to meet labor shortages, driving the trans-Atlantic slave trade.
Step-by-step explanation:
When Native Americans began dying in large numbers, the Portuguese responded by attempting to tighten control over the native population through various means. In 1549, the Portuguese Crown required that military efforts to subdue Native Americans be accompanied by evangelical campaigns aimed at converting them to Christianity. Decades later, laws were enacted to define the legal status of Indigenous people, allowing their enslavement only under specific conditions such as justification through a "just war" or the practice of cannibalism.
The contact between the Portuguese and the Native Americans often resulted in violence and enslavement, particularly with the forest peoples such as the Tupi. The Portuguese would attack and enslave the natives after bloody skirmishes. When the loss of native lives due to disease and conflict increased labor shortages, the Portuguese began importing enslaved Africans to meet labor demands, thereby contributing to the expansion of the trans-Atlantic slave trade.