Before the war crimes trials in 1945 under international law, war crimes, constituting violations of international humanitarian law that are criminalised, had first been incorporated into Article 228 of the 1919 Versailles Peace Treaty. After World War I, the Preliminary Peace Conference of Paris established the Commission of Responsibilities to enquire into some issues. One matter regarding the responsibility of the authors of the war is of relevance for my thesis. At the Paris Peace Conference, the United Kingdom submitted a Memorandum to the Commission on Responsibilities, on 13 February 1919. It proposed under Article III(1): “[t]hat an International Tribunal be established, […] for the trial and punishment of offences against the laws and customs of war and the laws of humanity.” In addition, Article V also provided that : “[w]hen the accused is found by the Tribunal to have committed an act in breach of the laws and customs of war or the laws of humanity with which he is charged, the Tribunal shall have the power to sentence him to such punishment as it shall think proper.” This proposal might be called the first draft statute of an international criminal court.[For the original source of this proposal, please see the document attached in the Blog The First Statute of an International Criminal Court?-By William Schabas]
It seems that the Commission of Responsibilities supported this idea and finally proposed an international court to be established while without any detailed plan. The US dissented with this proposal and it was rejected by the political leaders at the Conference. Furthermore, the Commission on Responsibilities also distinguished atrocities between war crimes, i.e., violations of the laws and customs of war, as opposed to offences committed by Germany and its Allies in their own territories against their own nationals, e.g., by the German against Jews subjects. It should be noted that the latter is not germane to the war crimes in internal armed conflict, but the “crimes against humanity and civilization”. However, it was not referred to in Articles 228-330 due to the strong objection of the US.
Luckily, the idea to prosecute individuals for war crimes was kept under Article 228 by national tribunals. Article 228 (1) of the Versailles Peace Treaty provided that: “[t]he German Government recognises 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. Such persons shall, if found guilty, be sentenced to punishments laid down by law. This provision will apply notwithstanding any proceedings or prosecution before a tribunal in Germany or in the territory of her allies.” (emphasis added). As we know, no German accused of war crimes had been tried by the Allies for a war crime. Few of them were tried and sentenced for mistreating prisoner of war in Leipzig under the German justice system. However, this Article is a reflection of the first attempt to prosecute individuals for war crimes between States at an international level. Though its outcome is not satisfying, it leads the trend to try individuals for violations of international law.
 Treaty of Peace between the Allied and Associated Powers and Germany [Treaty of Versailles], 28 June 1919, (1919) 2 Bevans 43.
 United Nations War Crimes Commission (ed), History of the United Nations War Crimes Commission and the Development of the Laws of War (London: HM Stationery Office 1948)