Blockade, the attempted prevention, by a fleet or squadron, lying off a town or a length of coast, of the ingress and egress of shipping. In order to be internationally recognised, a blockade must be effective. Otherwise, in accordance with the terms of the Declaration of Paris, it is not to be respected by neutrals. In any event it must be officially notified to neutral powers. It is generally believed that an effective blockade will in the future be difficult if not impossible to maintain, save by means of overwhelming forces.