§ 51. Intervention in a difference between two States is exercised through a communication of the intervening State to one or both of the conflicting States with a dictatorial request for the settlement of the conflict in a certain way, for instance by arbitration or by the acceptance of certain terms. An intervention can take place either on the part of one State alone or of several States collectively. If the parties comply with the request of the intervening State or States, the intervention is terminated. If, however, one or both of the parties fail to comply with the request, the intervening State will either withdraw its intervention or proceed to the performance of acts more stringent than a mere request, such as pacific blockade, military occupation, and the like. Even war can be declared for the purpose of an intervention. Of special importance are the collective interventions exercised by several great Powers in the interest of the balance of power and of humanity.[56] [Footnote 56: See above, vol. I. §§ 136 and 137.] [Sidenote: Time of Intervention.] § 52. An intervention in a difference between two States can take place at any time from the moment a conflict arises till the moment it is settled, and even immediately after the settlement. In many cases interventions have taken place before the outbreak of war between two States for the purpose of preventing war; in other cases third States have intervened during a war which had broken out in consequence of a conflict. Interventions have, further, taken place immediately after the peaceable settlement of a difference, or after the termination of war by a treaty of peace or by conquest, on the grounds that the conditions of the settlement or the treaty of peace were against the interests of the intervening State, or because the latter would not consent to the annexation of the conquered State by the victor.[57] [Footnote 57: With regard to the question of the right of intervention, the admissibility of intervention in default of a right, and to all other details concerning intervention, the reader must be referred above, vol. I. §§ 135-138.] PART II WAR CHAPTER I ON WAR IN GENERAL I CHARACTERISTICS OF WAR