The first thirty-five years after Mexico's independence were marked by political instability and the changing form of the Mexican State, from a monarchy to a federated republic.  There were military coups d'état, foreign invasions, ideological conflict between Conservatives and Liberals, and economic stagnation. Catholicism remained the only permitted religious faith and the Catholic Church as an institution retained its special privileges, prestige, and property, a bulwark of Conservatism. The army, another Conservative institution, also retained its privileges. Former Royal Army General Agustín de Iturbide, became regent, as newly independent Mexico sought a constitutional monarch from Europe.  When no member of a European royal house desired the position, Iturbide himself was declared Emperor Agustín I. The young and weak United States was the first country to recognize Mexico's independence, sending an ambassador to the court of the emperor and sending a message to Europe via the Monroe Doctrine not to intervene in Mexico.  The emperor's rule was short (1822–23) and he was overthrown by army officers.