Aerial Warfare.—The first time that aircraft played an im portant part was in the Great War when it co-operated with the land and sea forces and gave valuable help in the campaign against submarines, in the bombardment of enemy military ob jectives and, generally, in its use as a scout. Although there was a lack of rules in 1914 on the subject of aerial warfare, all of these services may be legitimately included amongst belligerent rights since they were directed against the armed forces of the enemy. There was, however, a grave abuse by Germany and Austria of these rights in the bombing by aeroplanes of unfortified, unarmed and defenceless towns and villages with severe loss to non-combatant life and property. The Hague Convention of Jurists, appointed under the terms of the Washington Conference of 1922, prepared in the following year a set of rules which par tially fill up the gap existing in the laws of aerial warfare. The rules prohibit aerial bombardment for the purpose of terrorising the civilian population, of destroying or damaging private property not of a military character or of injuring non-combatants or enforcing compliance with requisitions in kind or payment of contributions. They further enact that "aerial bombardment is legitimate only when directed at a military objective, that is to say, an object of which the destruction or injury would constitute a distinct military advantage to the belligerent."
War Crimes.—The many violations of the rules of warfare led to the suppression in the Treaties of Peace which terminated the Great War of the usual "amnesty clause" and to its substitution by an entirely novel principle, that of the punishment of war criminals. Article 228 of the Treaty of Versailles, 1919, provides that the "German Government recognizes the right of the Allied and Associated Powers to bring before military tribunals persons accused of having committed acts in violation of the laws and customs of war." The Allies acceded to the request of Germany that the accused persons should be tried by German Tribunals and accordingly sixteen cases were proceeded with and resulted in six convictions. These sentences were both insufficient and in adequate. The Advisory Committee of Jurists which sat at The Hague in 1920 to prepare the Statute for the Permanent Court of International Justice expressed a "voeu" for the creation of an International Court of Criminal Justice. A Statute for such a Court was elaborated at the Vienna Conference of the Interna tional Law Association, 1926, for an interstate Convention. Art. 16 of the Covenant of the League of Nations provides for the application of sanctions against members of the League which resort to war in disregard of their obligations.