When Freud worked with people with trauma (particularly the trauma experienced by soldiers returning from World War I), he observed that subjects often tended to repeat or re-enact these traumatic experiences, a phenomenon that Freud called repetition compulsion. This appeared to violate the pleasure principle, the drive of an individual to maximize his or her pleasure. Freud found this repetition of unpleasant events in the most ordinary of circumstances, even in children's play (such as the celebrated Fort/Da (Gone/There) game played by Freud's grandson, who would stage and re-stage the disappearance of his mother and even himself).