German officers and soldiers had gazed from the French coastline across the 20 miles of the English Channel which separated them from their enemy. To a man, they knew that the conquest of Great Britain would be their greatest challenge to date. However, they were brimming with confidence. Operation Sealion, as the forthcoming invasion was codenamed, would involve the marshalling of troops and equipment, as well as the rounding up of enough barges suitable for transporting the most formidable fighting machine in the world across the narrow expanse of the Channel. Still, all of the victories thus far, all of the planning and all of theFuhrer’s bold rhetoric meant far less without mastery of the skies. Control of the air was a perquisite to any successful invasion.