Invasion barges massed in Boulogne harbour, France, 1940 (1943). German invasion barges waiting on the French coast during the Battle of Britain. Operation Sea Lion was Nazi Germany's plan to invade the United Kingdom during World War II. From Coastal Command. [His Majesty's Stationery Office, London, 1943],Image: 262136380, License: Rights-managed, Restrictions: , Model Release: no