The reference to Article 11 in two of the articles of the Protocol (Articles 5 and 10) has advantages beyond those to which attention is drawn in the commentary on the text of those articles. It will be an incitement to science to clear the ground for the work which the League of Nations will one day have to undertake with a view to bringing about, through the development of the rules of international law, a closer reconciliation between the individual interests of its Members and the universal interests which it is designed to serve. 8.--DETERMINATION OF THE AGGRESSOR. _Article 10._ In order that the procedure of pacific settlement may be accompanied by the necessary sanctions, it has been necessary to provide for determining exactly the State guilty of aggression to which sanctions are to be applied. This question is a very complex one, and in the earlier work of the League the military experts and jurists who had had to deal with it found it extremely difficult. There are two aspects to the problem: first, aggression has to be defined, and, secondly, its existence has to be ascertained. The definition of aggression is a relatively easy matter, for it is sufficient to say that any State is the aggressor which resorts in any shape or form to force in violation of the engagements contracted by it either under the Covenant (if, for instance, being a Member of the League of Nations, it has not respected the territorial integrity or political independence of another Member {187} of the League) or under the present Protocol (if, for instance, being a signatory of the Protocol, it has refused to conform to an arbitral award or to a unanimous decision of the Council). This is the effect of Article 10, which also adds that the violation of the rules laid down for a demilitarised zone is to be regarded as equivalent to resort to war. The text refers to resort to war, but it was understood during the discussion that, while mention was made of the most serious and striking instance, it was in accordance with the spirit of the Protocol that acts of violence and force, which possibly may not constitute an actual state of war, should nevertheless be taken into consideration by the Council. On the contrary, to ascertain the existence of aggression is a very difficult matter, for although the first of the two elements which together constitute aggression, namely, the violation of an engagement, is easy to verify, the second, namely, resort to force, is not an easy matter to ascertain. When one country attacks another, the latter necessarily defends itself, and when hostilities are in progress on both sides, the question arises which party began them. This is a question of fact concerning which opinions may differ.