In case the Power not a party to this Covenant shall not accept the invitation of the Delegates to become _ad hoc_ a party, it shall be the duty of the Executive Council immediately to institute an inquiry into the circumstances and merits of the dispute involved and to recommend such joint action by the Contracting Powers as may seem best and most effectual in the circumstances disclosed. ARTICLE X If hostilities should be begun or any hostile action taken against the Contracting Power by the Power not a party to this Covenant before a decision of the dispute by arbitrators or before investigation, report and recommendation by the Executive Council in regard to the dispute, or contrary to such recommendation, the Contracting Powers shall thereupon cease all commerce and communication with that Power and shall also unite in blockading and closing the frontiers of that Power to all commerce or intercourse with any part of the world, employing jointly any force that may be necessary to accomplish that object. The Contracting Powers shall also unite in coming to the assistance of the Contracting Power against which hostile action has been taken, combining their armed forces in its behalf. ARTICLE XI In case of a dispute between states not parties to this Covenant, any Contracting Power may bring the matter to the attention of the Delegates, who shall thereupon tender the good offices of the League of Nations with a view to the peaceable settlement of the dispute. If one of the states, a party to the dispute, shall offer and agree to submit its interests and causes of action wholly to the control and decision of the League of Nations, that state shall _ad hoc_ be deemed a Contracting Power. If no one of the states, parties to the dispute, shall so offer and agree, the Delegates shall, through the Executive Council, of their own motion take such action and make such recommendation to their governments as will prevent hostilities and result in the settlement of the dispute. ARTICLE XII Any Power not a party to this Covenant, whose government is based upon the principle of popular self-government, may apply to the Body of Delegates for leave to become a party. If the Delegates shall regard the granting thereof as likely to promote the peace, order, and security of the World, they may act favourably on the application, and their favourable action shall operate to constitute the Power so applying in all respects a full signatory party to this Covenant. This action shall require the affirmative vote of two-thirds of the Delegates. ARTICLE XIII The Contracting Powers severally agree that the present Covenant and Convention is accepted as abrogating all treaty obligations _inter se_ which are inconsistent with the terms hereof, and solemnly engage that they will not enter into any engagements inconsistent with the terms hereof.