In 1815 the Congress of Vienna established the Grand Duchy of Luxembourg, an independent state under the sovereignty of the King of the Netherlands. The Treaty of London in 1867 declared the state to be neutral. The territory was invaded by Germany in the course of both World Wars. The constitution was amended in 1948 so that the requirement of neutrality was lifted, thus allowing Luxembourg to join NATO in 1949. Luxembourg was party to the Benelux economic union of 1948 and is a member of the European Union (EU).
