The Patriot War was an attempt in 1812 to foment a rebellion in Spanish East Florida with the intent of annexing the province to the United States. The invasion and occupation of parts of East Florida had elements of filibustering, but was also supported by units of the United States Army, Navy and Marines, and by militia from Georgia and Tennessee. The rebellion was instigated by General George Mathews, who had been commissioned by United States President James Madison to accept any offer from local authorities to deliver any part of the Floridas to the United States, and to prevent the reoccupation of the Floridas by Great Britain. The rebellion was supported by the Patriot Army, which consisted primarily of citizens of Georgia. The Patriot Army, with the aid of U.S. Navy gunboats, was able to occupy Fernandina and parts of northeast Florida, but never gathered enough strength to attack St. Augustine. United States Army troops and Marines were later stationed in Florida in support of the Patriots. The occupation of parts of Florida lasted over a year, but after United States military units were withdrawn and Seminoles entered the conflict, the Patriots dissolved.

East Florida was a colony of Great Britain from 1763 to 1783 and a province of the Spanish Empire from 1783 to 1821. The British gained control over Spanish Florida in 1763 as part of the Treaty of Paris that ended the Seven Years' War. Deciding that the colony was too large to administer as a single unit, British officials divided Florida into two colonies separated by the Apalachicola River; the colony of East Florida, with its capital located in St. Augustine and West Florida, with its capital located in Pensacola. East Florida was much larger and comprised the bulk of the former Spanish colony and most of the current state of Florida. It had also been the most populated region of Spanish Florida, but before control was transferred to Britain, most residents – including virtually everyone in St. Augustine – left the territory, with most migrating to Cuba.