Territorial integrity is the principle under international law that gives the right to sovereign states to defend their borders and all territory in them of another state. It is enshrined in Article 2(4) of the UN Charter and has been recognized as customary international law. Conversely it states that imposition by force of a border change is an act of aggression. In recent years there has been tension between this principle and the concept of humanitarian intervention under Article 73.b of the United Nations Charter "to develop self-government, to take due account of the political aspirations of the peoples, and to assist them in the progressive development of their free political institutions, according to the particular circumstances of each territory and its peoples and their varying stages of advancement." History of territorial integrity As far back as the earliest written records known, there have been political units claiming a definite territory. Intrusion into these territories was often considered an act of war, and normally resulted in combat. There were also sometimes several layers of authority, with units waging war on each other while both recognising some higher authority. Ancient and medieval nobility would fight private wars amongst while still acknowledging the same king or emperor, such as was case in the Spring and Autumn period in ancient China, when the Eastern Zhou Dynasty were nominal rulers. Supporters of the concept of Westphalian sovereignty consider that the modern idea of territorial integrity began with the Peace of Westphalia in 1648. However, ancient Chinese and ancient Indigenous cultures of North America and Australia, amongst others, contain diverse territorial understandings surrounding regional integrity. The League of Nations was intended to uphold territorial integrity and other principles of international law. It did condemn the Italian invasion of Ethiopia. It broadly supported the Chinese Republic over the creation of Manchukuo in Manchuria and eastern Inner Mongolia. Most historians say that the League was discredited by its failure to make these judgements effective. With the formation of the United Nations (UN) and, later, such organizations as the Conference on Security and Cooperation in Europe (now Organization for Security and Co-operation in Europe), territorial integrity became a part of international resolutions. The Helsinki Final Act dealt with both the inviolability of frontiers and the territorial integrity of States, among other things. In a changing world The recent (post-World War II) strict application of territorial integrity has given