The choice of this soldier was unfortunate. Personally ambitious
and cherishing in secret the thought of independence, Iturbide,
faithless to his trust, entered into negotiations with the
insurgents which culminated February 24, 1821, in what was called
the "Plan of Iguala." It contained three main provisions, or
"guarantees," as they were termed: the maintenance of the
Catholic religion to the exclusion of all others; the
establishment of a constitutional monarchy separate from Spain
and ruled by Ferdinand himself, or, if he declined the honor, by
some other European prince; and the union of Mexicans and
Spaniards without distinction of caste or privilege. A temporary
government also, in the form of a junta presided over by the
viceroy, was to be created; and provision was made for the
organization of an "Army of the Three Guarantees."

Despite opposition from the royalists, the plan won increasing
favor. Powerless to thwart it and inclined besides to a policy of
conciliation, the new viceroy, Juan O'Donoju, agreed to ratify it
on condition--in obedience to a suggestion from Iturbide--that
the parties concerned should be at liberty, if they desired, to
choose any one as emperor, whether he were of a reigning family
or not. Thereupon, on the 28th of September, the provisional
government installed at the city of Mexico announced the
consummation of an "enterprise rendered eternally memorable,
which a genius beyond all admiration and eulogy, love and glory
of his country, began at Iguala, prosecuted and carried into
effect, overcoming obstacles almost insuparable"--and declared
the independence of a "Mexican Empire." The act was followed by
the appointment of a regency to govern until the accession of
Ferdinand VII, or some other personage, to the imperial throne.