This "Rhea letter" became the innocent source of one of the most
famous controversies in American history. Jackson supposed that the
communication had been promptly delivered to Monroe, and that his plan
for the conquest of Florida had the full, if secret, approval of the
Administration. Instructions from the Secretary of War, Calhoun,
seemed susceptible of no other interpretation; besides, the conqueror
subsequently maintained that he received through Rhea the assurance
that he coveted. Monroe, however, later denied flatly that he had
given any orders of the kind. Indeed he said that through a peculiar
combination of circumstances he had not even read Jackson's letter
until long after the Florida campaign was ended. Each man, no doubt,
thought he was telling the truth, and historians will probably always
differ upon the merits of the case. The one thing that is perfectly
certain is that Jackson, when he carried his troops into Florida in
1818, believed that the Government expected him to prepare the
territory for permanent American occupation.

In early March, Jackson was at Fort Scott, on the Georgia frontier,
with about two thousand men. Though he expected other forces, Jackson
found that scarcity of rations made it inadvisable to wait for them,
and he therefore marched his army on as rapidly as possible down the
soggy bank of the Apalachicola, past the ruins of Negro Fort, into
Florida, where he found in readiness the provisions which had been
sent forward by way of Mobile. Turning eastward, Jackson bore down
upon the Spanish settlement of St. Marks, where it was rumored that
the hostile natives had assembled in considerable numbers. A small
fleet of gunboats from Mobile and New Orleans was ordered to move
along the coast and intercept any fugitives, "white, red, or black."
Upwards of two thousand friendly Indians joined the land expedition,