1. President James Buchanan was president of the United States right before Abraham Lincoln. So, upon hearing that the Mormons in Utah were practicing polygamy, and that Brigham Young, second president of the Church was governor of the territory, He decided that he had found a suitable scapegoat.
2. How did it end? Congress saw right through what President Buchanan was trying to do, and strongly opposed the Utah War. Senator Sam Houston was vehemently opposed to it and called it, "one of the most fearful calamities that has befallen this country, from its inception to the present moment.