[1] The remains of Fort Pupo are situated about three miles south of Green Cove Springs in Clay County, near the end of Bayard Point opposite Picolata.

A letter written by Royal Engineer Antonio de Arredondo on January 22, 1737 describes it as "a sentry box built of boards, eight feet in diameter… surrounded by a palisade.

[11][12] At the same time, James Oglethorpe, the governor of the British colony of Georgia, began building up a joint force of militia, regular troops, and Indians at Fort Frederica in preparation for a planned invasion of Florida.

Oglethorpe made his first move and invaded Spanish territory in late December 1739, his objective being to harass the Spaniards, burn their plantations, and intimidate their Indian allies.

The Spanish garrison at Fort Pupo spotted Oglethorpe's Indian auxiliaries from the other side of the river, and, thinking they were Yamasee allies, sent a ferry across, which hastily reversed course and returned when it perceived its mistake.

[17] Oglethorpe had successfully struck against the forts Pupo, Picolata, and San Diego during these preliminary raids, made in anticipation of his plan to capture and destroy St. Augustine by a land and sea attack.