http://www.atimes.com/atimes/Global_Economy/MC30Dj01.htmlThe 1648 treaty of Westphalia established the principle that nation states could run their internal affairs as they pleased - it was no longer acceptable for Catholic states to invade Protestant states because they didn't like their religion (or vice versa).
Westphalianism proved a vital organizing principle for the next 300 years, allowing significant periods of peace to appear between all the wars - and thus mankind's greatest boon, the Industrial Revolution, to become established. We now appear to be abandoning that principle - and the economic and political implications of doing so are dire.
The Westphalia principle always had a few holes around the edges. Colonialism resulted in frequent invasions of previously independent states, some of which were justified to change unacceptable domestic practices, whether fiscal (Egypt in 1882), economic (the Transvaal in 1899), or humanitarian (Spanish-American War, 1898). There were however few if any invasions of "rich" countries caused by their domestic policies and beliefs, although conquerors such as Napoleon used any unpalatable domestic policies of their victims as a further excuse for aggression if it suited them.
After the establishment of the United Nations in 1945, intervention that contravened Westphalian principles was deemed unacceptable even in countries that would previously have been considered ripe for colonial rule. The Anglo-French attack on Egypt in 1956 established this rule, being brought to a rapid halt by the United Nations resolutions and by threats against sterling.
The Soviet Union violated Westphalian principles by its invasions of Hungary (1956), Czechoslovakia (1968) and Afghanistan (1979), but the first two of those exceptions were already considered part of the Soviet bloc while Afghanistan, because of its backwardness, was something of a special case.
Similarly the United States in its invasions of the Dominican Republic (1965) and Panama (1989) was protecting the Western Hemisphere against Communism and the Panama Canal respectively - the domestic policies of the two countries were largely an excuse. Notably, the United States never invaded Cuba, even though the country was only 90 miles from Florida and its domestic policies were about as unacceptable as it's possible to get.
Since the 1989-91 breakup of the Soviet bloc, Westphalian principles have begun to lose their force. The 1991 Gulf War was scrupulous, some would say over-scrupulous, in observing them - the Allies attacked Saddam Hussein to remove him from Kuwait, but failed even in the flush of victory to remove him from office, though by the practices of previous wars they would have been justified in doing so. In 1992, the US invaded Somalia for humanitarian reasons - and was forced to leave in humiliating failure. In 1994, it invaded Haiti for humanitarian reasons - and installed a tyrant Jean-Betrand Aristide worse than any who had gone before in even Haiti's unhappy history.
Again in 1995 the United States intervened ineffectively in Bosnia, where Croatian president Franjo Tudjman, once allowed to arm the Croatian forces, had already done most of the hard work. Following that invasion, the US imposed a peace, the Dayton Accords, which have kept the peace but through incompetent meddling by global aid agencies have prevented Bosnia from establishing a viable economy. In 1999, the United States again intervened in Yugoslavia for humanitarian reasons, creating a new country, Kosovo, that appears to be becoming an Islamic terrorist state in the heart of Europe. See link
