Carleton's march into New Mexico has already been described in connection with the mining boom of Arizona. The silver mines of the Santa Cruz Valley had drawn American population to Tubac and Tucson several years before the war; while the confederate successes in the upper Rio Grande in the summer of 1861 had compelled federal evacuation of the district. Colonel E. R. S. Canby devoted the small force at his command to regaining the country around Albuquerque and Santa Fé, while the relief of the forts between the Rio Grande and the Colorado was intrusted to Carleton's California Column. After May, 1862, Carleton was firmly established in Tucson, and later he was given command of the whole Department of New Mexico. Of fighting with the confederates there was almost none. He prosecuted, instead, Apache and Navaho wars, and exploited the new gold fields which were now found. In much of the West, as in his New Mexico, occasional ebullitions of confederate sympathizers occurred, but the military task of the commanders was easy. The military problem of the plains was one of police, with the extinction of guerrilla warfare and the pacification of Indians as its chief elements. The careers of Canby, Carleton, and Gilpin indicate the nature of the western strategic warfare, Schofield's illustrates that of guerrilla fighting, the Minnesota outbreak that of the Indian relations. In the Northwest, where the agricultural expansion of the fifties had worked so great changes, the pressure on the tribes had steadily increased. In 1851 the Sioux bands had ceded most of their territory in Minnesota, and had agreed upon a reduced reserve in the St. Peter's, or Minnesota, Valley. But the terms of this treaty had been delayed in enforcement, while bad management on the part of the United States and the habitual frontier disregard of Indian rights created tense feelings, which might break loose at any time. No single grievance of the Indians caused more trouble than that over traders' claims. The improvident savages bought largely of the traders, on credit, at extortionate prices. The traders could afford the risk because when treaties of cession were made, their influence was generally able to get inserted in the treaty a clause for satisfying claims against individuals out of the tribal funds before these were handed over to the savages. The memory of the savage was short, and when he found that his allowance, the price for his lands, had gone into the traders' pockets, he could not realize that it had gone to pay his debts, but felt, somehow, defrauded. The answer would have been to prevent trade with the Indians on credit. But the traders' influence at Washington was great. It would be an interesting study to investigate the connection between traders' bills and agitation for new cessions, since the latter generally meant satisfaction of the former.