time restricted to male heirs by the Nassau Family Pact) passed to Adolph of Nassau-Weilburg.
During World War I Luxembourg was invaded and occupied by Germany, but was allowed to maintain its independence and political mechanisms.
During World War II, Luxembourg was unable to maintain its policy of neutrality when in 1940 Nazi Germany invaded and occupied the country, due to its strategic location on the invasion route into France. In contrast to the First World War experience, Luxembourg was treated as a Germanic territory and informally annexed to an adjacent province of the Third Reich in 1940. A government in exile based in London fought alongside the Allies, sending a small group of volunteers who participated in the Normandy invasion. Luxembourg was liberated in September 1944. It became a founding member of the United Nations in 1946, and of NATO in 1949.
In 1957, Luxembourg became one of the six founding countries of the European Economic Community (later the European Union), and, in 1999, it joined the euro currency era. In 2005, a referendum on the EU treaty establishing a constitution for Europe was held in Luxembourg
