The Battle of the Atlantic was the longest continuous military campaign of World War II, running from 1939 until the defeat of Nazi Germany in 1945, and spanning a significant portion of naval history. The Battle of Britain was the first major military campaign fought entirely by air forces. In the Battle of the Atlantic, the Allies gradually gained the upper hand. Operation Sea Lion was Germany s code name for its planned invasion of the United Kingdom and was to have taken place during the Air Battle of Britain. I used the board game "A World at War" by GMT Games. In the scenario to be tested, after the conquest of France in June, in December 1940, Hitler issued a directive to intensify preparations for an invasion of Great Britain, operationally combining the naval battle of the Atlantic with the air battle of England.