In 1857 President Buchanan quietly sent new officials to rule the Utah Territory and replace Brigham Young as the territorial governor. With no official announcement, the new leaders were accompanied by a twenty-five-hundred-member troop under the leadership of Col. Albert Sidney Johnston. The secrecy, the size of the military force, and past experiences caused the Mormons to mistakenly believe they were about to be invaded by the federal government. Utah's territorial militia, the Nauvoo Legion, readied itself against the impending invasion until disagreement and disapproval in Washington finally led to successful diplomacy and a reluctant peace. LeRoy R. and Ann W. Hafen have brought together the principal official documents pertaining to these singular and nearly tragic events as well as excerpts from the diaries and journals of the central figures, speeches given in Congress and in Utah, and pertinent correspondence.