Final answer:
Coronado required a large expedition for military protection. The Castillo de San Marcos was built to defend against imperial challengers. Caravansaries were sponsored by governments to support and protect trade along major routes.
Step-by-step explanation:
Francisco Vázquez de Coronado needed so many people to accompany him on his expedition primarily for military protection. The size and composition of his expeditionary force reflect the dangers of the unknown territories and the potential hostility from Indigenous populations they might encounter. The 16th-century explorations were perilous, and a substantial force offered the best chance of survival and success.
The Spanish built Castillo de San Marcos to defend against imperial challengers. Located in St. Augustine, Florida, the fort was designed to protect Spanish interests in the area from other European powers who might attempt to encroach upon Spain's claimed territories in the New World.
Governments in states along trading routes may have sponsored caravansaries to facilitate commerce and protect caravans. These establishments provided a place for merchants and their caravans to rest and resupply, which was essential to maintaining the flow of trade along major land routes.