The Utah war was inglorious. Far from its base, and operating in a desert against plainsmen of remarkable skill, the army was helpless. At will, the Mormon cavalry cut out and burned the supply trains, confining their attacks to property rather than to armed forces. When the army reached Fort Bridger, it found Brigham still defiant, his people bitter against conquest, and the fort burned. With difficulty could the army of invasion have lived through the winter without aid. In the spring of 1858 a truce was patched up, and the Mormons, being invulnerable, were forgiven. The army marched down the trail again.
The Mormon hegira planted the first of the island settlements in the heart of the desert. The very isolation of Utah gave it prominence. What religious enthusiasm lacked in aiding organization, shrewd leadership and resulting prosperity supplied. The first impulse moving population across the plains had been chiefly conquest, with Oregon as the result. Religion was the next, producing Utah. The lust for gold followed close upon the second, calling into life California, and then in a later decade sprinkling little camps over all the mountain West. The Mormons would have fared much worse had their leader not located his stake of Zion near the point where the trail to the Southwest deviated from the Oregon road, and where the forty-niners might pay tribute to his commercial skill as they passed through his oasis on their way to California.
On his second exploring trip, John C. Frémont had worked his way south over the Nevada desert until at last he crossed the mountains and found himself in the valley of the Sacramento. Here in 1844 a small group of Americans had already been established for several years. Mexican California was scantily inhabited and was so far from the inefficient central government that the province had almost fallen away of its own weight. John A. Sutter, a Swiss of American proclivities, was the magnate of the Sacramento region, whence he dispensed a liberal hospitality to the Pathfinder's party.
In 1845, Frémont started on his third trip, this time entering California by a southern route and finding himself at Sutter's early in 1846. In some respects his detachment of engineers had the appearance of a filibustering party from the start. When it crossed the Rockies, it began to trespass upon the territory belonging to Mexico, with whom the United States was yet at peace. Whether the explorer was actually instructed to detach California from Mexico, or whether he only imagined that such action would be approved at home, is likely never to be explained. Naval officers on the Pacific were already under orders in the event of war to seize California at once; and Polk was from the start ambitious to round out the American territory on the Southwest. The Americans in the Sacramento were at variance with their Mexican neighbors, who resented the steady influx of foreign blood. Between 1842 and 1846 their numbers had rapidly increased. And in June, 1846, certain of them, professing to believe that they were to be attacked, seized the Mexican village of Sonoma and broke out the colors of what they called their Bear Flag Republic. Frémont, near at hand, countenanced and supported their act, if he did not suggest it.