Which task of the soldiers at a presidio was most important

Presidios were local military forts that were customized to the needs of the soldiers whose most important task was to protect against Islamic armies in Africa, and later Atlantic Pirates and indigenous warriors of the Americas.  The Presidio soldiers were further assigned roles to protect the missions, conduct supply trains, escort missionaries, colonists, and merchants, carry mails, and explore the country.

is there answer chooses?