The Battle of Britain was a continued attack by the Luftwaffe on Great Britain during the summer and the autumn of 1940.

Overview 
Its first objective was to get control of the air space above Britain from the Royal Air Force (RAF), especially the Fighter Command.

The name comes from a famous speech, which was delivered by British Prime Minister Winston Churchill in the House of Commons: "The Battle of France is over. I expect the Battle of Britain is about to begin...."

The Battle of Britain was the first major campaign to be fought only by air forces, and it was also the largest and longest aerial bombing campaign until then.

Part I: Strategic targets 
In July 1940, coastal shipping convoys and shipping centres, such as Portsmouth, began to be the main targets. A month later, the Luftwaffe shifted its attacks to RAF airfields and infrastructure, which were other useful war targets. As the battle progressed the Luftwaffe also targeted aircraft factories and ground infrastructure.

Coastal radar stations were bombed and so for a time, only one radar mast was standing. The British used a backup system of human observers to get information to the headquarters of Fighter Command. Most historians agree that part of the campaign went into Germany's favour.

Part II: Civilian targets 
Eventually the Germans switched to attacking population centres, such as towns and cities, as well as factories. After the RAF bombed Berlin, and German air force bases in France, Hitler cancelled his orders not to bomb population centres and ordered attacks on British cities.p305 The attacks on civilians were terror bombing tactics designed to cause panic and damage morale.

On 7 September 1940, a massive series of raids with nearly 400 bombers and more than 600 fighters targeted docks on the Thames in London day and night.

The RAF 11 Group rose to meet them in greater numbers than the Luftwaffe expected; 12 Group's Big Wing took 20 min to gain formation and missed its intended target, but it came across another formation of bombers while it was still climbing. The delay was blamed on being requested too late.

The Luftwaffe began to abandon its morning raids, with attacks on London starting late in the afternoon for 57 nights of attacks in a row.

Fighter Command had been suffering low morale since it was short of men and machines, and the break from airfield attacks allowed it to recover and so week by week, the defenders were getting stronger, and the losses suffered by the Luftwaffe were growing.

On 15 September, two massive waves of German attacks were prevented by the RAF, with every aircraft of 11 Group being used that day. The total casualties on that important day were 60 German and 26 RAF aircraft shot down. The German defeat caused Hitler to order two days later a delay of the preparations for the invasion of Britain. In the face of increasing losses in men, aircraft and the lack of good replacements, the Luftwaffe later switched from daylight to night-time bombing.

On 27 September, a Junkers Ju 88 returning from a raid on London was shot down in Kent. The German airmen survived to fight a battle against British troops stationed locally. That was said to be the first time in nearly 300 years that armed invaders had fought with British soldiers on British soil.

Dowding system 
The keystone of the British defence was the detection, command, and control, which ran the battle. It was called the 'Dowding System', after its chief architect, Air Chief Marshal Sir Hugh Dowding, the leader of RAF Fighter Command.

The core of the system was the use of Radio Direction Finding (RDF, later called radar, for radio detection and ranging). Its use, as we as by information by the Royal Observer Corps, was crucial and allowed the RAF to intercept the incoming German aircraft.

Radar operators were linked via telephone, whose wires were laid deep underground with concrete anti-bomb protection,p47 to an operational centre. The centre was Fighter Command Control at Bentley Priory. During the battle, several Coastal Command and Fleet Air Arm units came under Fighter Command control.

Fighters
The Germans' Messerschmitt Bf 109E and 110C squared up against the British workhorse Hawker Hurricane Mk I and the less numerous Supermarine Spitfire Mk I. The Bf 109E had a better climb rate and was 10 to 30 mph faster than the Hurricane, depending on the altitude.p266 In September 1940, the more powerful Mk IIa series 1 Hurricane started entering service but only in small numbers. That version was capable of a maximum speed of 342  mph, 25 to 30  mph faster than the Mk I.

The performance of the Spitfire during the Dunkirk evacuation came as a surprise although the German pilots retained a strong belief that their 109 was the superior fighter. However, the Bf 109E had a much larger turning circle than either the Hurricane or the Spitfire. The two British fighters had eight Browning 303 machine guns, but most Bf 109Es had two machine guns and two wing cannons. The Bf 109E and the Spitfire were superior to each other in key areas. For instance, at some altitudes, the Bf 109 could outclimb the British fighter.

Aftermath 
The failure of Germany to achieve its objectives of destroying Britain's air defences or forcing Britain to negotiate an armistice or an outright surrender is considered to be its first major defeat and one of the crucial turning points in the war.p388

If Germany had gained air superiority, Adolf Hitler might have launched Operation Sea Lion, his planned invasion of Britain.

References 

1940 in Europe
1940s in the United Kingdom
Britain
Britain
Britain
Britain
Britain