The Mexican Frontier, 1821–1846 published by other historians. This work was supplemented by additional primary materials which he discovered in the archives that allowed him to delve further into certain areas. "The Mexican Frontier" examines the southwestern United States, specifically the areas now known as Arizona, California, New Mexico, and Texas, in the twenty-five years between Mexico's independence from Spain and the beginning of the Mexican–American War. This resulted in the transfer of control of the border areas to the United States. In the early days of the Republic of Mexico, these areas comprised its northern border, including the territories of Alta California and
Direct colonial rule Direct colonial rule Direct colonial rule is a form of colonialism that involves the establishment of a centralized foreign authority within a territory, which is run by colonial officials. According to Michael W. Doyle of Harvard University, in a system of direct rule, the native population is excluded from all but the lowest level of the colonial government. Ugandan academic Mahmood Mamdani classifies direct rule as centralized despotism: a system where natives were not considered citizens. The opposite of direct colonial rule is indirect rule, which integrates pre-established local elites and native institutions into the administration of the colonial government.