Obligation to settle disputes peacefully
The peaceful settlement of international disputes is a fundamental principle of international law, and a direct corollary of the prohibition on the threat or use of force. Both principles feature prominently in the 1945 Charter of the United Nations (UN Charter). They have been repeated on many occasions, including the UN General Assembly's 1971 Declaration on Principles of International Law Concerning Friendly Relations and Co-operation among States in Accordance with the Charter of the United Nations and the 1982 Manila Declaration on the Peaceful Settlement of Disputes between States.
Prior to the 20th century it was quite legitimate for States to use armed force to settle their international disputes. Conquest was an accepted means by which States could acquire territory. Gradually, however, as the power and efficiency of weaponry increased, public opinion began to shift and formal attempts began to limit the legitimacy of warfare as a tool for dispute resolution. Even prior to World War I, in 1899 and 1907, conventions were concluded at The Hague restricting the right to wage war and seeking to establish peaceful dispute resolution mechanisms. The Permanent Court of Arbitration was established through these treaties, providing a neutral forum in which States could settle their differences.
The need for peaceful dispute resolution mechanisms was even more apparent after World War I. The creation of the League of Nations as a forum for international discussion and cooperation, and the Permanent Court of International Justice (PCIJ) as the first permanent judicial body designed to hear disputes between States, laid the foundation for the international community accepting the significance of measures designed to ensure peaceful settlement of international disputes.