Much of the language of diplomatic intercourse is a matter of “common form”. It has evolved its own characteristic idiom, a significant part of which derives from Latin and French, the two main languages that for centuries were used by diplomats of different countries as “tools of their trade”. The heritage of elaborate phraseology has been retained in the formal usage of the United Kingdom and of some other European countries, where it is felt to express with clarity and due emphasis ideas, which have remained basic to diplomacy throughout the centuries.

During the Middle Ages and at the beginning of modern times diplomatic negotiations were conducted in Latin, which was then the language common to all civilised Christian powers. French came next in frequency of use. Henry VI of England wrote to Charles VII of France in French, and that language was usually employed both in writing and speaking between the two countries.

The French language starts seriously to question the supremacy of Latin in international diplomacy in the seventeenth century. The debates of the Treaties of Westphalia (1648) showed the insufficiency of Latin: its vocabulary had not developed, while its pronunciation varied so much from one country to another that it ceased to be a practical means of communication. Negotiators were therefore led to the use of modern languages. For instance, the Treaty of 30 January 1648 between Spain and the United Provinces, by which the independence of the latter was recognized, was in French and Dutch.

Apart from the decline of spoken Latin, there were a number of other factors contributing to the elevation of French in the seventeenth century. It had been since the sixteenth century the common language of European high society. Many important principles of diplomacy as a science of international relations were laid down in French by the French. Cardinal Richelieu was the first statesman to recognize diplomacy as a continuing process involving permanent negotiations between nations. His other beliefs are largely those practised by diplomatic services and government today: that policies should be based on pragmatic national interest; that allies should be chosen because of their permanence, not because they are liked; and that ambassadors should have a single chief. He saw that foreign affairs in France were handled by one Ministry.