Throughout history, military forces often relied on civilian conscripts, often yanked forcibly from their homes and farms to fight for wars they didn't understand. Wiser military leaders saw the folly in this. Men such as Gustavus Adolphus turned to professional soldiers trained to fight at a moment's notice. Like the samurai of feudal Japan or the US Rangers of 20th century America, these special forces units traded higher costs during peacetime for a state of constant readiness.