This June, the Chalke Valley History Festival is marking the seventieth anniversary of D-Day with a number of talks and displays, but also an air show spread over both days of the weekend. D-Day may have been launched on 6th June 1944, but for the Allied air forces, the preparations for the invasion began a lot earlier, and even once the beaches had been taken and the bridgehead secured, those same air forces continued to play a critical role. As the Germans had quite correctly realised in 1940, when they were looking to invade Great Britain, having command of the skies was a prerequisite for any seaborne invasion. That still held just as true for the Allies in 1944, and had been achieved in spectacular fashion.

By the summer of 1944, the RAF had been bombing Germany for four years. It had been a long, bitter battle, that had disproved pre-war predictions that air power alone could end a war. In the early years of the war, bombing had proved nothing like as accurate as had been originally thought and bombers considerably more vulnerable, but by the middle of 1943, with the arrival of new navigational and bombing aids and with the advent of large numbers of four-engine heavy bombers – and particularly Lancasters – the impact of the strategic air offensive against Germany was beginning to take hold. In July 1943, over three consecutive nights, the northern port and major city of Hamburg was hammered by some 3,000 aircraft, causing a firestorm that ripped the heart out of the city and left some 40,000 dead. And it came on top of a series of raids on the Ruhr industrial heartland and the destruction of Germany’s two largest and iconic dams.

By that time, the US Eighth Air Force was also making a considerable contribution to the battle. While the RAF bombed at night, the US Eighth Air Force sent over streams of B-17 Flying Fortresses over by day – operating on the theory that they were sufficiently robust, armoured and armed to fend off any German attacks by fighter aircraft. This, however, proved woefully over-optimistic; the Americans, like the British before them, had to learn the hard way that heavy bombers were neither as well protected as thought nor as accurate in their bombing as hoped. Losses to Allied bomber crews in the autumn of 1943 were horrendous – so bad, in fact, that the Eighth was losing 30% of its crews every month.

The big problem was that Bomber Command was suffering from attacks by much improved German night fighters, while the Eighth were realising that without fighter escort all the way to the target, their Flying Fortresses were easy prey for the German fighter planes. An American marine fighting in the worst battles in the Pacific had a better chance of survival than US Eighth Air Force bomber crews in the last months of 1943.

Even so, however horrendous the losses to Allied aircrews, the Luftwaffe’s position was even worse. There was a shortage of fuel, and a shortage of aircraft, but most of all, there was a shortage of pilots and increasingly, especially well-trained pilots, and flying instruction was repeatedly cut in an effort to keep up with demand. By the autumn of 1943, the Luftwaffe was losing 15% of fighter pilots a month, a loss rate they could in no way sustain. To extend the comparison, a young German was more likely to survive fighting on the Eastern Front than becoming a fighter pilot.

Moreover, defending the Reich was costing Germany in many other ways. War production may have been increasing under the direction of Albert Speer, but it was costing Germany a lot more to achieve this, thanks to the huge dispersal of resources and factories due to Allied bombing. Every train used to transport materials and parts around the disparate armament factories of the Reich was a train that could not be used supplying the front. Furthermore, by early 1944, there were some 15,000 heavy anti-aircraft guns in Germany manned by 500,000 men – both of which would have been of incalculable benefit at the front, whether in Russia or along the Atlantic Wall; there were just 32 heavy guns along the Normandy coast on D-Day.

And the Luftwaffe had also pulled back nearly all its fighter force into Germany and away from the front, which was of enormous benefit to the planners of Operation OVERLORD, the invasion of Normandy.

However, it was clear to the commanders of the Allied Combined Bomber Offensive that the rate of losses suffered in 1943 could not continue. Unless bombers could be escorted all the way to Germany, they would have to restrict operations to the radius in which Allied fighter aircraft could operate. That would mean loosening the noose and risking the rehabilitation of the Luftwaffe’s fighter force, neither of which augered well for the forthcoming invasion of Northern France.

The solution came from an unlikely source in the shape of the North American P-51 Mustang, originally procured by the British and designed, built and first flown in an astonishing 117 days. However, with its Allison engine, it initially proved very unremarkable. Its transformation occurred when engineers and test pilots at Farnborough, the RAF’s main research establishment, realised it had extraordinary aerodynamic qualities and that when fitted with a Rolls-Royce Merlin, was utterly transformed. By adding an expendable fuel tank, this now magnificent fighter aircraft was given an unbeatable range, allowing it to escort the Fortresses all the way to Berlin and beyond.

By the beginning of 1944, US Eighth Air Force had a force of over 1,000 B-17s, more than 400 of the robust and very fast P-47 Thunderbolt, and well over 300 Mustangs. The Eighth’s new commander, General Jimmy Doolittle, recognised there was now an opportunity to effectively destroy the Luftwaffe once and for all. Bad weather hindered plans throughout January, but finally, on 20th February 1944, the skies cleared – and stayed clear too. In what became known as ‘Big Week’, four separate thousand bomber raids very effectively struck the Luftwaffe’s main production bases. At the same time, the fighter escorts – and especially the Mustangs – took on the German fighters as they rose up to meet the threat. In February, the Luftwaffe lost 33% of its single-engine fighters and nearly 18% of its pilots. The air fighting continued into March, when the Germans suffered 56% losses in fighter planes and a further 22% of its pilots. It was a battle of attrition the Luftwaffe could not sustain. In January they had had 2,395 fighter pilots, but over the next five months lost 2,262 – in other words, almost 100% of the number they started with. By the time of D-Day, there were simply almost no properly trained pilots left.

In addition to destroying the fighter arm of the Luftwaffe, the Allies also carried out a highly effective assault on German transportation in the nine weeks leading up to D-Day. Some 195,000 sorties were flown and 197,000 tonnes of bombs dropped. By this time, RAF Bomber Command, especially, had developed the capability to achieve highly accurate bombing; the days of 1940-1941, when 75% of bombs dropped landed at least five miles from the target had long gone. Attacks on bridges, marshalling yards and even locomotives themselves were astonishingly effective, so much so that over the last week of May 1944, Allied air attacks destroyed no less than 500 locomotives. Since by this time Germany had precious little fuel, they were heavily dependent on rail to transport almost everything, but especially tanks and guns. By late May, rail traffic was reduced to 55% capacity from January’s level and then, once the Seine bridges were destroyed at the very end of the month, to just 30%. ‘The railway network is completely wrecked,’ noted a German report of 3rd June. ‘Paris has been systematically cut off from long-distance traffic and the most important bridges over the lower Seine had been destroyed.’

Another aspect of Allied air power was reconnaissance. Photo reconnaissance Spitfires, especially, played a very important role. To help protect intelligence gathered by the cryptanalysts at Bletchley Park, the entire Atlantic Wall, all the way from Norway to southern France, was very obviously photographed. The work done by these PR Spitfires was particularly important over Normandy. The meticulously analysed photographs helped pinpoint enemy defences to an astonishing level of detail, which in turn enabled the attacking forces to prepare for what ahead.

Nor did the work end with D-Day. Air power continued to play a critical role, first and foremost in delaying the arrival of the German panzer divisions – the best equipped and trained units in France – to the front. It took the Das Reich Division most of June to reach the front, 17th Panzer Grenadier Division five days to travel 200 miles, and the Panzer Lehr, arguably the best division in the entire Wehrmacht, suffered horribly en route to the Caen area. They had been based at Le Mans on D-Day, but as General Fritz Bayerlein, commander of the division later confessed, ‘It took two days and one night to reach the Caen front, and, on 7 June 44, I lost 85 or 86 armoured vehicles, 123 trucks, 5 tanks and 23 prime movers, all through air bombings by Jabos [fighter bombers].’ Bayerlein, who had fought in North Africa and had experience the rise of Allied air power first hand, was under no doubt about the effect they had on the Battle for Normandy. When asked immediately after the war what he thought the main German failings were in Normandy, he replied simply, ‘Completely wrong evaluation of the effects of the Allied air operations.’

The bombing operations in support of the landings were largely a failure, but the operations further inland not only restricted movement, but also saw some crucial targets hit, not least the Headquarters of Panzer Group West. The hugely able General Erich Marks, commander of LXXXIV Corps, was killed on 12th June by an Allied air strike, while Rommel himself, commander of Army Group B in the west, was badly wounded by Spitfires of 602 Squadron on 17th July. But one of the striking aspects of the air effort over Normandy is the way in which the Allies were constantly striving to improve.

Perhaps the greatest example of this was the American development of what became known as ‘Armoured Column Cover’, or ACC. Two problems quickly emerged from the dense bocage fighting in the American sector. First, columns of vehicles still had to use the narrow, winding tracks and roads that criss-crossed the countryside, which channelled them into a narrow corridor and made them very vulnerable to any hidden enemy position waiting around the corner. The second was making sure that when called into help, fighter-bombers hit the right target at the right time.

Leading the way in finding a solution was Brigadier-General ‘Pete’ Quesada, commander of the IX Tactical Air Command. In Italy, Allied tactical air forces had already developed ‘cab ranks’ of fighters constantly airborne, and ‘Rover Davids’ consisting of a air ground controller and an army forward observation officer. Quesada now took this a level further by placing an experienced pilot on the ground in a tank connected via VHF radio to the fighter-bombers in the sky above. The fighters and the armoured column were now in direct contact. Up above, the pilot could warn the column below of any upcoming enemy positions, while the men on the ground could call in far more specific air strikes, and, more importantly, ensure a precise and agreed time on target. From the moment the Americans began to burst through the German defences at the end of July, this new innovation proved a huge advantage.

The coup de grace of the Normandy campaign was also largely carried out by Allied air forces. As the German defences finally crumbled, the remnants of the Fifteenth and 5th Panzer Armies desperately tried to escape what became known as the Falaise Pocket. Funnelled into a a handful of narrow roads, these toe-to-tail columns of panzers, trucks, horses and carts proved rich pickings, especially for the RAF’s rocket-firing Typhoons.

This June’s Chalke Valley History Festival will be recognising the huge contribution air power made to the Normandy campaign with a series of displays from a number of aircraft that played such an important role. Not only will there be a pair of Spitfires, but also the game-changing P-51 Mustang, that workhorse of the US bombing effort, the B-17 Flying Fortress, the Dakota, and also a PR Spitfire too. And welcoming those coming to see this spectacular show will be a Rolls-Royce Merlin engine on display, the power plant that enabled the Mustang to realise its full potential.