Initially established and manned by peninsular Spanish regulars in 1765 as an infantry battalion to occupy Luisiana, acquired from France three years earlier, what would ultimately become the veteran and professional Regimiento de Infantería de Luisiana formed the core of Spain's military establishment in Louisiana and, later, in the Spanish Floridas until it faded into oblivion during the terminal period of Spain's colonial tenure in North America.
Reorganized after its arrival in North America in 1769, the battalion's detachments performed garrison duties at outposts in Spanish Louisiana as far north as Illinois. In 1779, when Spain joined France in an alliance against England during the American War for Colonial Independence, the unit was enlarged to regimental strength through the addition of a second battalion and participated with distinction in the 1779-1781 conquest of then-British West Florida under the leadership of Louisiana Governor Bernardo de Gálvez. Spain's official repossession of Florida by the terms of the 1783 Treaty of Paris resulted in a third battalion being added to the regiment for service in the Floridas in 1786. This seemingly impressive force was, however, a "paper tiger." It never achieved its newly authorized strength in manpower, nor did it enjoy adequate supplies of material provisions to properly maintain itself.