The bombing before the invasion

At the beginning of May 1944, a month before the Normandy landings, Allied aircraft were carrying out the most intensive bombing yet seen in Western Europe over France and Belgium. By night hundreds of bombers of the British Bomber Command came over marshalling yards, engine sheds and railway workshops; by day the same and other targets were attacked by American heavy bombers of the Eighth Air Force, medium bombers and fighter-bombers of the Ninth Air Force, and British tactical aircraft. Ammunition dumps, armoured training camps, airfields, coastal artillery batteries and radar stations were also hit, and from 7 May the bridges over the Seine as well.

Popular chronologies record under 6 May “heavy Allied bombing of the Continent in preparation for D-Day”. This was not a single raid, however, but a state of affairs that lasted from March until the invasion itself and peaked in May. The word “Continent” also needs narrowing: the pre-invasion offensive was directed above all at France and Belgium, while the strategic bombing of Germany and its allies went on in parallel.

The Transportation Plan in practice

The basis of the preparations was the Transportation Plan, adopted at the end of March 1944 after a long dispute. Its author was the scientific adviser Solly Zuckerman, and its champions were the Deputy Supreme Commander, Air Chief Marshal Arthur Tedder, and the commander of the Allied Expeditionary Air Force, Air Chief Marshal Trafford Leigh-Mallory. The premise was simple: the Germans would defend the coast with divisions brought by rail from the interior of France, Belgium and the Reich, so the network on which they would travel had to be smashed in advance – several dozen (some 80 on the original list) of the largest junctions, marshalling yards and repair works in northern France and Belgium. Bomber Command’s first attacks on marshalling yards, including Trappes, came at the beginning of March, and from 14 April 1944 the heavy bombers of both nations operated under the direction of General Dwight Eisenhower, the Supreme Allied Commander, and his SHAEF headquarters.

By early May the plan was in full swing. Air Chief Marshal Arthur Harris, who that winter had still been arguing that his night bombers were unsuited to hitting small targets and were better used against German cities, had to admit that reality had exceeded his fears. New target-marking methods – the Oboe radio navigation system, de Havilland Mosquitos marking the target from low level, and a “master bomber” directing the raid by radio – allowed the Lancasters and Halifaxes to put their bombs on the tracks with an accuracy that no one would have expected of them in 1943. According to the Bomber Command operational diaries (Middlebrook and Everitt), on the night of 1/2 May British bombers attacked, among other targets, the railway workshops at Chambly near Paris and junctions in Belgium, and on the night of 6/7 May the station at Mantes-Gassicourt on the Seine and ammunition dumps in western France. Each night brought similar lists of targets: Lille, Ghent, Kortrijk, Hasselt, Leuven (Louvain), Boulogne.

The Americans operated by day. Carl Spaatz’s heavy bombers – the B-17s and B-24s of the Eighth Air Force – divided their effort between the Reich and the marshalling yards of France and Belgium. B-26 Marauder and A-20 medium bombers of the Ninth Air Force and P-47 Thunderbolt fighter-bombers attacked junctions, bridges and airfields closer to the coast, while the Fifteenth Air Force in Italy reached targets in the south of France. All of this was part of the wider preparations for D-Day.

Bridges, batteries and radars

The Transportation Plan aimed to wreck the rail network deep inland, but the tactical air commanders also wanted to seal off the future battle area itself. The natural barrier was the Seine: below Paris there was no bridge across it that did not matter for German supplies to Normandy. For a long time, however, steel and stone bridges were considered too difficult a target – staff calculations spoke of hundreds of tons of bombs per bridge. A trial settled the matter. According to the official US Army Air Forces history (Craven and Cate), on the morning of 7 May 1944 a few P-47 Thunderbolt fighter-bombers of the Ninth Air Force dive-bombed the railway bridge at Vernon and destroyed it; the little town itself suffered in the process. From that day on the Seine bridges became one of the main targets of the tactical air forces. The later course of that campaign, and the mass hunt for locomotives at the end of May, belong to a later stage of the story.

The second group of targets was the fortifications of the Atlantic Wall. Coastal artillery batteries, especially heavy guns in concrete casemates, could sink landing ships as they approached the beaches, and radar stations could detect the approaching fleet. Attacks on the batteries had been going on since April, and in May the tactical air forces – above all British rocket-armed Hawker Typhoons – began systematically destroying the radars along the coast from Belgium to Brittany. Secrecy, however, demanded that the Germans should not be able to read the landing site from a map of the raids. A rule was therefore adopted, which historians cite from AEAF documents: for every target attacked in the area of the future invasion, at least two were attacked outside it, mainly in the Pas-de-Calais department, where the Germans expected the main blow. The bombing thus became part of Operation Fortitude – the deception campaign intended to confirm Field Marshals Gerd von Rundstedt and Erwin Rommel in their belief that the Allies would land at the narrowest point of the English Channel. The cost of this rule was high: for every ton of bombs that fell on Normandy, two fell elsewhere, and with them the toll among the inhabitants of northern France rose.

Mailly-le-Camp

The bloodiest raid of those weeks for the airmen themselves was the attack on the armoured training camp at Mailly-le-Camp in Champagne on the night of 3/4 May 1944. It housed a school and depot through which the German armoured units stationed in France passed – a target important to the invasion preparations and at the same time far from any large centres of population. Bomber Command dispatched 346 Lancasters and 14 Mosquitos. The target was marked accurately, but because of radio interference the master bomber was unable for a long time to call the main force in to attack, and the bombers circled over the assembly point. German night fighters had time to arrive. The British lost 42 Lancasters – 11.6 per cent of the aircraft dispatched – and about 300 airmen. Some 1,500 tons of bombs fell on the camp, destroying barracks, workshops and much of the equipment and killing and wounding many German soldiers. According to surviving accounts, not a single French civilian was killed in the raid itself; a few local people suffered only when a shot-down bomber crashed onto a house.

The cost to civilians

It was quite different in the towns where the marshalling yards lay. Railway junctions were usually in working-class districts or on the outskirts, and even accurate bombing meant that part of the load fell on the houses around the tracks. The most notorious example was the raid on La Chapelle on the northern edge of Paris on the night of 20/21 April 1944, in which some 640–670 people were killed. May brought further such tragedies – in France and in Belgium, where residents of nearby streets were also killed during night raids on junctions around Ghent, in Kortrijk and in Leuven.

Even when the Transportation Plan was adopted, staff estimates spoke of tens of thousands of French and Belgian dead and wounded, and the most pessimistic calculations of as many as some 100,000. Winston Churchill feared that such a price would alienate for years the very nation the Allies were to liberate, and demanded that the number of French civilians killed should not exceed about 10,000; Tedder was to keep him informed of the running total. The dispute was still going on in May. On 7 May 1944 the Prime Minister put his concerns to President Franklin Delano Roosevelt, who replied on 11 May that he regretted the civilian losses but did not intend, from so far away, to impose restrictions on the commanders that might jeopardise the success of Overlord. Eisenhower kept the plan, while agreeing to concessions: some targets in densely built-up areas were struck off or postponed, attacks were made in good visibility, and residents were warned by leaflets and BBC broadcasts to keep away from the tracks.

The final toll remains disputed. The British researchers Lindsey Dodd and Andrew Knapp, adding up the victims of the individual pre-invasion raids, arrived at a figure of just under 11,000 dead in France – close, therefore, to the threshold set by Churchill; other estimates, which also include targets in the south of the country, put it at about 15,000. To these must be added the victims in Belgium. Vichy and German propaganda exploited every such raid, portraying the airmen as murderers. Even so, the Resistance did not break with the Allies, and French railwaymen were themselves preparing to sabotage the network at the moment of the landing.

The Luftwaffe under pressure

The precondition for the whole offensive was command of the air, and the Allies had won it in the first months of 1944. After Big Week in February and the daylight raids on Berlin in March, American long-range fighters – P-51 Mustangs, P-47s and P-38s – not only escorted the bombers but also hunted German fighters in the air and on their airfields. The Luftwaffe was losing aircraft, and above all experienced pilots, faster than it could train replacements. According to the American historian Williamson Murray, in May 1944 alone roughly a quarter of Germany’s fighter pilots were killed or wounded. The Reich also had to keep most of its fighters for the defence of its own cities, so in France Field Marshal Hugo Sperrle’s Luftflotte 3 had only a few hundred serviceable aircraft. Allied bombers over France and Belgium had to reckon chiefly with anti-aircraft fire and night fighters – as Mailly-le-Camp painfully showed – but not with any organised daylight defence.

At the same time the commander of the US Strategic Air Forces in Europe, Carl Spaatz, argued that the quickest way to paralyse the Wehrmacht was to strike at German fuel. Eisenhower agreed to a few days of such attacks in May, seeing them also as a way of drawing the Luftwaffe into battle. On 12 May 1944 several hundred heavy bombers of the Eighth Air Force attacked synthetic fuel plants in central Germany, among them Leuna near Merseburg, Böhlen and Zwickau. The armaments minister Albert Speer wrote in his post-war memoirs that the technological war was decided on that day. It was the beginning of the oil offensive, which over the following months deprived Germany of most of its aviation fuel production.

Place in the war

The pre-invasion bombing did not last a single day, nor did it end in May. After 21 May the tactical air forces began a massive hunt for locomotives and trains; by the day of the invasion every bridge over the Seine between Paris and the sea had been destroyed or damaged, and in the last days before the landing the bridges over the Loire were hit as well. At the end of May American bombers from Italy attacked junctions in Lyon, Saint-Étienne and Marseille, where several thousand civilians were killed. Within a few weeks tens of thousands of tons of bombs fell on the railways of France and Belgium.

The effects became clear after 6 June 1944. German divisions brought to Normandy travelled by rail along roundabout routes, unloaded far from the front and covered the last tens, sometimes hundreds, of kilometres by night on the roads, under fire from Allied fighter-bombers. A German Air Ministry report of 13 June 1944 spoke of traffic having broken down on all the main lines and of the coastal defences being cut off from their supply bases. Historians still argue over whether the greater share in this success belonged to the destruction of marshalling yards, as Tedder and Zuckerman wanted, or to the cutting of bridges and the attacks on trains championed by their critics; they agree that together they paralysed German logistics in the decisive weeks.

The pre-invasion offensive was thus the last stage of the preparations for D-Day and for Overlord: first command of the air was won, then communications were shattered, and finally the coastal defences were blinded. The price was paid by French and Belgian civilians too – before the invasion itself well over ten thousand of them were killed, counting the Belgians – and by Allied airmen: according to frequently cited figures, between April and early June the Allied air forces lost some 2,000 aircraft and about 12,000 men. That price is today a permanent part of the memory of the liberation of France, alongside the memory of the Normandy landings themselves.