Treaties form the basis of most parts of modern international law. They serve to satisfy a fundamental need of States to regulate by consent issues of common concern, and thus to bring stability into their mutual relations. As an instrument for ensuring stability, reliability and order in international relations, treaties are one of the most important elements of international peace and security. This is why, from the earliest days in the history of international law, treaties have always been the primary source of legal relations between entities today known as States. The Preamble of the VCLT itself emphasizes the fundamental role of treaties in the history of international relations and especially the importance of treaties for developing peaceful co-operation among nations. This fundamental importance of treaties proved to be a continuum, while the rules and procedures of treaty-making, as well as the contents of international agreements, changed through the centuries.