If there were, in reality, no need of an army in Mexico to oppose a foreign enemy, or, to preserve domestic peace, one would still be required to secure the Northern Frontier against the incursions of Indians. From the earliest periods, the Spaniards were vexed by their savage assaults, and, since the establishment of independence, the Mexicans have every year seen their people and property carried off by the robber tribes, whilst their villages, _ranchos_ and _haciendas_ were totally destroyed or partially ravaged. Mexican engineers have calculated that the new boundary line, following the course of the Rio Grande and the Gila and including a mathematical line of seventy leagues between these streams, is six hundred and forty-six leagues or about nineteen hundred miles in length. Three-fourths of this line pass through an uninhabited region, and, consequently, the savages have free access across it to the few and small settlements on the border. Such an extent of frontier, though considerably reduced from the former line anterior to the treaty, became at once an object of concern to the government, especially as the people of the United States immediately opened communications through the Indian country with the Pacific, and would probably soon control the important passes through the whole region north of the boundary. Accordingly on the 20th of July, 1848, it was decreed that eighteen MILITARY COLONIES should be created, and placed within easy communication, so as to protect the southern settlers in some degree, or to encounter and punish the savages in their forays. The greater portions of the most warlike tribes were transferred by the treaty to the United States, and, by one of its articles, we bound ourselves to aid, at least, in saving the Mexicans from their plunder if we could not totally destroy their inimical power. In the neighborhood of the boundary, from near the mouth of the Gila to the commencement of the mathematical line, before alluded to, we find the tribes known as Coyotes, Mimbreños and Gileños, the former of whom wage war against Sonora, whilst the latter attack Chihuahua. The Apaches and Cumanches spread their numerous hordes from the vicinity of Chihuahua to the sources of the Nueces, twenty-five leagues beyond the Rio Grande. Besides these, there are, throughout this district many savage bands, supporting themselves entirely by the chase, and it is probable, according to the opinion of soldiers and captives, who have been among the tribes, that all these clans can unite thirty thousand warriors, whilst they still leave a sufficient number to protect their wigwams and villages.