Suez Crisis
1956. Military conflict between Britain, France and Israel on one side, and Egypt on the other.
Background
Gamal Abdel Nasser, the President of Egypt, had decided to nationalise the Suez Canal. These plans conflicted with British interests, both economically (Britain owned shares in the Suez Canal Company) and geopolitically (the idea of the Empire still dominated political decisions, and Northern Africa was considered a zone of stratetic interest).
Significance
The international community, and particularly the United States, disapproved of Britain going it alone; the country had to withdraw its troops after a short while. Apparently, Britain had been relegated to the status of a second-rate power; when the Soviet Union invaded Hungary to squash the Hungarian Revolution (almost simultaneously), the world did not care, or dare, to intervene.