The U.S. Army expedition of 1849 clearly illustrated this problem. Lt. Col. John W. Washington, military commander of New Mexico, led an expedition to Canyon de Chelly, then considered to be the Navajo heartland. Washington met local Navajo chiefs on the crest of a small hill between the present Thunderbird Guest Ranch and the mouth of the canyon. Here on Treaty Hill a treaty of “lasting peace” was signed with the Indians. Washington had no sooner returned to Albuquerque, however, than he learned that another Navajo band had raided a small village near Santa Fe. [Illustration: Col. E. R. S. Canby led the last campaign against the Navajos before the Civil War.] Regardless of treaties and punitive expeditions, Navajo depredations continued. Late in 1851, Col. E. V. Sumner marched into the Navajo country in still another effort to settle the problem. After a single encounter with the Navajo in Canyon de Chelly, Sumner returned to a spot southwest of the Chuska Mountains where he established Fort Defiance in the autumn of 1851. Fighting broke out again in 1858, when a Negro slave of the post commander at Fort Defiance was killed by a Navajo arrow. The Army retaliated with an attack on a party of peaceful Navajos, and the Indians retreated northward. Up to this time, U.S. Army commanders had controlled Indian policies; the authority of the civil agents appointed by the Indian Department was negligible. But now the civilian agents brought political pressure to bear upon the unsuccessful Army. To soothe the politicians, the Army drew up still another treaty with the Navajos on December 25, 1858. This treaty was the second attempt to outline the boundaries of a proposed Navajo reservation. Like an earlier proposal, the Meriweather Treaty of 1855, it was never ratified. The year 1859 was relatively peaceful, with few raids on either side. But the next year opened with a series of Navajo raids that culminated in a concentrated attack on Fort Defiance. Some of the old Navajos who participated later recalled that it was a carefully planned assault at dawn, with as many as 2,000 warriors taking part. After attacking for two hours, the Indians were forced to withdraw. In the winter of 1860-61, Col. E. R. S. Canby led the last military expedition against the Navajos before the Civil War, but his efforts failed to bring peace. Zarcillos Largos, a great Navajo leader who had worked for more peaceful relations with whites, was killed in an ambush during the campaign. The Indians soon resorted to their old tactic of dispersing, and the campaign ended with another treaty. When troops were withdrawn from Fort Defiance in March 1861 for Civil War duty, the last restraint was removed from both sides, and raiding began once more. For the Spanish-Americans, it was the high point of their warfare against the Navajos.