The mandate system was established under Article 22 of the Covenant of the League of Nations, entered into on 28 June 1919.
With the dissolution of the League of Nations after World War II, it was stipulated at the Yalta Conference that the remaining Mandates should be placed under the trusteeship of the United Nations, subject to future discussions and formal agreements.
The US failed to ratify the Treaty of Versailles which included the Covenant of the League of Nations so the US never joined the League.
Peace treaties have played an important role in the formation of the modern law of nations.
The first twenty-six articles of the Treaty of Versailles contained the Covenant of the League of Nations.
The article called for such people's tutelage to be "entrusted to advanced nations who by reason of their resources, their experience or their geographical position can best undertake this responsibility".
All of the territories subject to League of Nations mandates were previously controlled by states defeated in World War I, principally Imperial Germany and the Ottoman Empire.
Article 22 was written two months before the signing of the peace treaty, before it was known what communities, peoples, or territories were related to sub-paragraphs 4, 5, and 6.
The treaty was signed, and the peace conference had been adjourned, before a formal decision was made.The mandates were arrangements guaranteed by, or arising out of the general treaty which stipulated that mandates were to be exercised on behalf of the League.The treaty contained no provision for the mandates to be allocated on the basis of decisions taken by four members of the League acting in the name of the so-called "Principal Allied and Associated Powers".It contained the international machinery for the enforcement of the terms of the treaty.Article 22 established a system of Mandates to administer former colonies and territories.have reached a stage of development where their existence as independent nations can be provisionally recognized subject to the rendering of administrative advice and assistance by a Mandatory until such time as they are able to stand alone.