During World War II, Iceland gained strategic significance due to its proximity to Europe and North America. When Germany invaded Denmark in April 1940, Britain realized the importance of preventing a similar invasion of Iceland and decided to occupy the island. However, their occupation was short-lived, as they had to return to defend against Germany's planned attack on the United Kingdom.
British Prime Minister Winston Churchill sought help from President Franklin D. Roosevelt to safeguard Iceland. In response, the United States sent Marines to Iceland five months before officially entering the war.