§ 27. War is very often enumerated among the compulsive means of settling international differences. This is in a sense correct, for a State might make war for no other purpose than that of compelling another State to settle a difference in the way required before war was declared. Nevertheless, the characteristics of compulsive means of settling international differences make it a necessity to draw a sharp line between these means and war. It is, firstly, characteristic of compulsive means that, although they frequently consist of harmful measures, they are neither by the conflicting nor by other States considered as acts of war, and consequently all relations of peace, such as diplomatic and commercial intercourse, the execution of treaties, and the like, remain undisturbed. Compulsive means are in theory and practice considered peaceable, although not amicable, means of settling international differences. It is, further, characteristic of compulsive means that they are even at their worst confined to the application of certain harmful measures only, whereas belligerents in war may apply any amount and any kinds of force, with the exception only of those methods forbidden by International Law. And, thirdly, it is characteristic of compulsive means that their application must cease as soon as their purpose is realised by the compelled State declaring its readiness to settle the difference in the way requested by the compelling State; whereas, war once broken out, a belligerent is not obliged to lay down arms if and when the other belligerent is ready to comply with the request made before the war. As war is the _ultima ratio_ between States, the victorious belligerent is not legally prevented from imposing upon the defeated any conditions he likes. [Sidenote: Compulsive Means in contradistinction to an Ultimatum and Demonstrations.] § 28. The above-described characteristics of compulsive means for the settlement of international differences make it necessary to mention the distinction between such means and an _ultimatum_. The latter is the technical term for a written communication by one State to another which ends amicable negotiations respecting a difference, and formulates, for the last time and categorically, the demands to be fulfilled if other measures are to be averted. An _ultimatum_ is, theoretically at least, not a compulsion, although it can practically exercise the function of a compulsion, and although compulsive means, or even war, can be threatened through the same communication in the event of a refusal to comply with the demand made.[29] And the same is valid with regard to withdrawal of diplomatic agents, to military and naval demonstrations, and the like, which some publicists[30] enumerate among the compulsive means of settlement of international differences. Although these steps may contrive, indirectly, the settlement of differences, yet they do not contain in themselves any compulsion.