The Monroe Doctrine.

In 1823, the United States issued what came to be known as the Monroe Doctrine. The Doctrine is interesting (and important) for two reasons: first, it is the first post-establishment diplomatic expression of independence and a loud demand for acknowledgement of U.S. (increasing) power and, second, it is disguised under a thin veil of moral argumentation. It is named after the President of the U.S., James Monroe — although the actual Doctrine was largely authored by John Quincy Adams, just a few years before his assumption of the Presidency of that country.

But why is the Monroe Doctrine of interest? Well, I find it exceptionally well-thought out as: 1) it succeeded in remaining coherent with what became the U.S. foreign policy until the early 20th century and 2) it managed to largely conceal what that policy entailed by employing morality, when the U.S. policy was essentially as contradicting as the moral grounds upon which the doctrine was issued: The Doctrine and its acceptance by the Europeans granted the U.S. unlimited reign over the American continents — and led to the introduction of its own form of colonialism-sans-occupation, viz. Manifest Destiny — while, for a considerable period of time it convinced part of the world with the moral argument in favour of freedom and independence.
Ironically, I feel that in my lifetime it is China, India, or some bloc encompassing the two that might issue a similar Doctrine, expressing their belief that the U.S. should stop ‘colonising’ (and interfering) with their continent and business.
As far as Europe is concerned, two centuries after the Monroe Doctrine was issued, the roles are reversed: it is the United States that has the role of the once mighty European Powers. Quite frequently one reads of the U.S. ‘recommendations’, ‘support’, ‘frustration’ with clearly European affairs, such as the enlargement, EU financial, military or other relations with other countries of even internal states. The U.S. has a large military and financial presence in Europe and frequently abuses its position on the world stage to further their aims, be they financial, political or military.
Despite its logical and moral shortcomings, the Monroe Doctrine is as elegant and intelligent as very few of the U.S. diplomatic maneuvers of the 20th century and stands in stark contrast to most post WWII U.S. foreign policy decisions that typically indicate no effort by their authors, to morally or logically ground U.S. decisions beyond the least intelligent, educated and questioning among us. While that might be due to factors beyond the U.S. such as the vastly different distribution of power in 1823 that required tact and true diplomacy on the part of the U.S. as well as the de facto diplomatic style imposed by the less straightforward, more sophisticated Europeans at that time, the doctrine remains an excellent example of diplomatic expression in the post-Iraq world of the early 21st century.