In the summer of 1940 the Germans were poised to invade Britain, but first they had to win control of the skies – taking on the fighter pilots of the RAF.
After Dunkirk there were only about 70 working tanks in Britain. In June, the British army had just 54 anti-tank guns.
However, the German high command had not expected such an overwhelming victory in France and were not sure what to do next.
As a new, 24-volume series of books charting the history of the Second World War explains, it was not until July 16 that Hitler issued Fuhrer Directive No 16 setting out the possibility of an invasion of Britain codenamed Operation Sea Lion.
The problem with transporting an invasion force across the English Channel was the strength of the Royal Navy so, as World War II – The Battle of Britain (the third volume in the series) point out, the only way the navy could be stopped from inflicting carnage on German invaders before they got ashore was through command of the air.
Hermann Goring, the flamboyant head of the Luftwaffe, thought he could destroy British Fighter Command in four days. He believed the victory the Luftwaffe had won in the air over France would be repeated.
And so the Battle of Britain was played out in the skies over southern Britain with key bases at Tangmere and Westhampnett on the outskirts of Chichester.
And, of course, the heroes of those dogfights were the Spitfire and the Hurricane fighter aircraft.
At the beginning of June 1940 the RAF had only 331 fighters but public appeals soon had British factories producing 500 of both aircraft a month compared to the 140 a month made by the Germans.
During the battle 352 Spitfires were lost and shot down 529 enemy aircraft.
The Spitfire, designed by Reginald Joseph Mitchell in Southampton, has become part of British folklore and just last weekend 10 of them flew together at the Goodwood Revival. It marked the 75th anniversary since the first one flew from Eastleigh airport and was believed to be the largest number to fly together since the Second World War.