British preparations
While the military authorities struggled to make good post-Dunkirk deficiencies, the Royal Air Force (RAF) was preparing to meet the Luftwaffe (German air force) under the overall command of Air Chief Marshal Sir Hugh Dowding. They were not starting from scratch: during the interwar years an integrated air defence system had been developed. As constituted in June 1940, Fighter Command was organised in three groups: Air Vice-Marshal Keith Park’s No. 11 Group covering the southeast; No. 12 Group (Air Vice-Marshal Trafford Leigh-Mallory) covering the midlands; and No. 13 Group (Air Vice-Marshal Richard Saul) covering the north. The German occupation of France soon led to a modification: another group, No. 10 Group, was constituted to cover the southwestern flank; it was commanded by Air Vice-Marshal Sir Christopher Brand. The fighter planes of these groups were supported on the ground by 1000 heavy and 700 light anti-aircraft guns and 1500 barrage balloons.
The main problems were a shortage of aircraft and pilots, exacerbated by losses in France and Norway. At the outset of the battle Dowding had just 644 fighters. Of the RAF’s nominal 52 squadrons, some had been lost altogether, others were exhausted, and 11 were converting to new aircraft. Only 28 combat-ready squadrons were available, 23 of them equipped with the most modern fighters, Supermarine Spitfires and Hawker Hurricanes. With aircraft production not meeting targets, the prospect of attrition was worrying. About 1000 pilots were available, a number that allowed little margin to cover losses. The RAF did enjoy one major advantage: since the battle was fought mainly over British territory, pilots who baled out or crash-landed were often able to rejoin their units. Damaged aircraft could also sometimes be recovered.
The RAF had several other advantages. First, its main fighter planes, the Spitfire and the Hurricane, were excellent machines, more than a match for the main German fighter, the Messerschmitt Bf 109, except at very high altitudes. Second, the RAF had the benefit of a recent major scientific advance - radar, a development whose importance the Germans initially under-estimated. The network of 52 radar stations on the coast of Britain provided timely warning of the build up of German concentrations over France. Park used this information, backed by sightings of the Air Observer Corps once the enemy planes crossed the coast, to good effect to deploy his limited resources. This direct intelligence was backed by information derived from the British ability, since April 1940, to read deciphered German operational messages - the so-called ULTRA intelligence.
German preparations
In contrast to the longstanding British air defence preparations, the German armed forces faced a daunting and unexpected task. They initially regarded the landing as akin to a large river crossing, with the Luftwaffe providing the bombardment support with its dive bombers, especially the Junkers Ju 87 (Stuka). But the Germans needed to assemble an invasion fleet capable of transporting a large force. British intelligence soon detected the build-up of barges and other craft in ports opposite the British Isles. These concentrations would be targeted by the RAF in an important, but costly, side bar to its effort in the battle. Both Coastal and Bomber Commands, in which hundred of New Zealanders were serving, carried out bombing raids against port facilities and communication hubs.
The German air effort against Britain would be made by three air fleets (Luftflotten) deployed in the newly conquered territories. The northern-most was Air Fleet 5, arrayed in Denmark and Norway. It was not well placed to attack Britain, given the distance involved; fighters did not have the range to accompany bombers all the way to targets from these bases. It was, however, a threat that the British could not ignore, ensuring that squadrons could not be stripped from No. 13 Group to assist further south. The brunt of the German effort would be borne by Air Fleet 2 in the Low Countries and Air Fleet 3 in northern France. Altogether, these two air fleets had 2600 aircraft, of which 1200 were twin-engine bombers and 760 single-engine fighters.
In mounting the air campaign, the Luftwaffe faced some distinct disadvantages. In the first place, its bomber aircraft, the Heinkel He 111, the Dornier Do 17 and Junkers Ju 88, were essentially medium bombers, with relatively small bomb loads. Designed to support the Wehrmacht (German army) they were not well suited to the type of strategic campaign now required. More seriously, the main German single-engine fighter, the Messerschmitt Bf 109, had limited range, ensuring that it could only spend about quarter of an hour over Britain before heading home or risk ditching in the Channel. This reduced the protection the fighters could give the bombers. The vaunted two-engine Messerschmitt Bf 110 fighter quickly proved incapable of mixing it with the RAF fighters.
