Since the end of the Cold War, private contractors have become more prevalent in zones of conflict. Both political and legal scholars highlight the multiple challenges this has introduced when tracing the responsibility of crimes in the field. Some, such as Martha Lizabeth Phelps, go as far to claim that if hired contractors are indistinguishable from national troops, the contractors borrow the state's legitimacy. The command responsibility of actions in warfare become increasingly unclear when actors are viewed as being part of a state's force, but are, in truth, private actors.