Final answer:
The Spanish fort of Castillo de San Marcos helped Spanish colonists in St. Augustine fend off attacks from rival European countries through its strategic location and strong military presence.
Step-by-step explanation:
The Spanish fort of Castillo de San Marcos helped Spanish colonists in St. Augustine fend off attacks from rival European countries by providing a strategic location for defense and having a strong military presence.
The fort's strategic location on the eastern coast of Florida allowed the Spanish to keep a watchful eye on incoming ships and defend against any attacks.
The fort's strong military presence, including cannons and a well-trained garrison, acted as a deterrent to rival European countries, making it more difficult for them to successfully attack and conquer St. Augustine.