When Charles I of England, Scotland, and Ireland was executed for treason against the state of England, much of the world and a large portion of England was appalled. Executing a sovereign was an unheard of event, but it also happened after a series of events that made it clear Charles would be executed. Charles was tried by a High Court of Justice, which was assembled by the "Rump Parliament." The Rump Parliament was the smaller Parliament of England that existed after Pride's Purge, a culling of the opponents of the New Model Army by Colonel Thomas Pride. That Parliament was the successor of the Long Parliament, which first met five years before and was the inciting element of the English Civil War. The English Civil War pitted Royalist forces against Parliamentary forces, with Parliament winning decisively. When Charles tried to change the terms of the end of that Civil War, he was basically saying he would declare war against Parliament. So they arrested him, tried him for treason, and executd him.