During the American Civil War, the Union Army consisted of a very small contingent of pre-war U.S. Army or "Regular Army" personnel combined with vast numbers of soldiers in state volunteer regiments raised and equipped by the States before being "federalized" and led by general officers appointed by the President of the United States and confirmed by the United States Senate. In many ways, these regiments resembled and might be analogized to the modern day National Guard. Due to their pre-war experience, they were considered by many to be the elite of the Union Army, and during battles regular army units were often held in reserve in case of emergencies.