Permanent neutrality is quite another thing. History shows that there are certain countries, certain geographical zones, which, by virtue of their situation, are in some way predestined to become periodically the theater of struggles between nations. The subjection of such a country to the exclusive influence of one great power has always marked a breakdown of the European balance of power. The idea of placing these zones by means of a treaty in the position of countries outside the possible zone of international conflicts corresponds to a general plan of establishing a régime of peace on the basis of reciprocal and voluntary restriction of action. From this point of view, neutralization is essentially a factor for peace. It follows that the state which is perpetually neutral has not only its own individual meaning and independent mission, but is an important “wheel” in the general policy. This is the case with Belgium, as it was established by the great powers after the revolt of 1830, and that is the true meaning of the statement that it was to be “perpetually neutral.” Between the neutralized state and the creators of its neutrality there thus exist reciprocal obligations. The contracting powers between them undertake engagements whereby they guarantee to the neutralized state the privileged condition of enjoying permanent peace; while on the other side, the neutralized state accepts the obligations which protect the European balance of power. In that way, each of the contracting powers is bound not to attack the neutral state; not to invite it to abandon its peaceful attitude; to defend it against any power, co-contracting or not, which would compel it to abandon its neutrality. The inviolability of the neutralized territory is agreed upon by this means, for violation would mean for such a state a breach of its own neutrality. On the other hand, the neutralized state must itself defend its neutrality, and adopt all the measures needed for such defense. For this reason, international law holds that a neutralized state which commits an act of defense is not to be considered as being in state of war with the power which violates its neutrality.[23] Moreover, the neutral state must prevent troops or convoys of a belligerent power from passing through its territory.[24] Finally, such a state ought to remain a truly independent state, for if it places or allows itself to be placed in a position of dependence upon another power it destroys the European balance of power, the origin of its international status. Some authorities on international law[25] maintain that in case of violation of the neutral territory by a belligerent, the contracting powers have not only the right, but the duty, to interfere _ex officio_, and to protect the neutral state by military power, even without the consent of the latter. On this point, however, opinion is divided.