"This is a Negro War, Not an Indian War." wrote Major General Thomas Sydney Jesup in frustration for having to fight a War he opposed.
By the time Florida became a U.S. Territory (in 1821), Blacks had been escaping into Florida to escape slavery for 130 years (since 1687). They first lived as allies of the Spanish in St. Augustine and later as allies, friends, and partners of the Seminoles.
By 1830, Florida had become both a Slave based 'cotton and cane' economy and a refuge for escaped Slaves living with the Seminoles. Southern Whites grew intensely angry over the loss of their 'Property' (the escaped Black Slaves) and pathologically fearful of slave insurrection assisted by Indian Warfare.
By 1835, Blacks in Florida were ready to fight and die with the Seminoles for their Freedom. They knew Slavery would not be abolished willingly in their lifetime. They knew they could expect no mercy from the Whites if they were captured. They had nothing to lose, but to fight alongside the Seminoles.