However, one thing is always in common: the move to power is almost always done clandestinely, except maybe in the final phases of a coup. He might have pulled off a classical coup.
He might have managed to kill the previous holder while the rightful heir is unable to respond. The Usurper might have managed to drive out the rightful holder in disgrace. But someone with a lesser claim, or no claim at all, in some way manages to grab the position. There is a rightful holder of some position of authority � the throne, the presidency, the chairmanship of a company, or something else.
