During World War II, Iceland joined Denmark in asserting neutrality. After the German occupation of Denmark on 9 April 1940, the Althing replaced the King with a regent and declared that the Icelandic government would take control of its own defence and foreign affairs. A month later, British armed forces conducted Operation Fork, the invasion and occupation of the country, violating Icelandic neutrality. In 1941, the Government of Iceland, friendly to Britain, invited the then-neutral United States to take over its defence so that Britain could use its troops elsewhere.