Relatively recent, multilateral diplomacy, meaning it is conducted between three or more states, has become essential in the 20th century.
Precedents as ancient as those in bilateral negotiations can be found in multilateral negotiations: from the 15th century sovereigns sent ambassadors to councils. The famous Westphalia Treaties signed in 1648 concluded a conference that had lasted for five years. The Vienna Congress of 1815 is the first in a series that were to make Metternich famous. However, it was not until nearly the middle of the century that states felt the need to meet, apart from exceptional political circumstances, to deal jointly with questions of common interest relating to new fields: for example the creation of the Universal Postal Union in 1874. In 1948, this doyen of international organisations became a "specialist institution" of the United Nations. It aimed to set up a single postal area for exchanging correspondence between member countries.
Metternich: He was Minister of Foreign Affairs and later the Chancellor of Austria (1821). He spent his career defending the monarchic Europe of 1815 against the rise of liberalism, which in 1848 resulted in him being driven out of power.
It began expanding rapidly after the First World War, when the hope that open and joint diplomacy would bring a definitive peace was put into practice with the creation of the League of Nations. The movement accelerated in the second half of the century and has continued to increase before our very eyes. In fact, it responds to two current trends that have already been underlined: international affairs are increasingly interconnected and they continue to concern even more, if not all, countries. Henceforth, faced with a new situation, the reflex is to establish an informal group of those states most interested in dealing with it.
Figures on multilateral diplomacy: France maintains 17 permanent representations to international organisations and 4 delegations to international bodies.
The congresses of the past broke up once their mission was completed, however the 20th century has seen long term international organisations being created: the UN, the European Union. The conferences convened to tackle particular problems negotiated a convention and then realised that it was necessary to monitor its application. To undertake this task the tendency is to create a new permanent organisation: in 1973, the Conference on Security and Co-operation in Europe, meeting in Helsinki, became in 1994 the organisation of the same name, the OSCE. In the same way, GATT has become the WTO.
The founding fathers of the League of Nations believing that diplomacy conducted "in the public domain" would preserve peace more effectively than traditional diplomacy conducted in secret. To some extent, multilateral diplomacy responds to this desire. Debates in the UN are public, risking being just for the sake of appearances. However, in practice everyone knows that the meetings of the Security Council are preceded by unofficial discussions, during which confidential negotiations reassert themselves.
In reality, multilateral diplomacy operates in a more collective than parliamentary way. Plenary assemblies bring all delegations together, sometimes in public, but in general only confirm the result of behind the scene deals between groups of states that are united by different affinities. It is here that the ingenuity of diplomats is exercised.
The increase in the power of multilateralism is a feature of our times, which opens up new fields of action for diplomacy.