OVERLORD

OVERLORD as the overall codename for the Allied invasion of occupied north-west Europe (see Maps 81 and 82). The assault phase of OVERLORD, the Normandy landings and associated operations, was codenamed NEPTUNE.

The Casablanca conference convened in January 1943 (see SYMBOL), gave the initial impetus to planning and executing OVERLORD by agreeing to establish a planning staff, COSSAC, and to increase the build-up of US troops in the UK (BOLERO). COSSAC, aided by earlier plans for other incursions on to the Continent, sought a suitable landing area in the Low Countries or France which was within range of Allied fighters, where the beach defences could be neutralized, and where the rate of build-up of Allied troops could equal that of the defending German forces. This last depended on the immediate capture of a major port, but as it was supposed that it would take three months to put any port into working order, it was necessary to find firm and sheltered beaches over which the troops ashore could be supplied for at least 90 days, and which had an adequate road network behind them. COSSAC eventually chose the Baie de la Seine, between Le Havre and the Cherbourg peninsula, because it fitted the necessary criteria and was close to a major port, Cherbourg, which could, it was hoped, be captured almost immediately. All supplies were to be landed over the beaches, via artificial harbours (see MULBERRIES), while fuel was to be pumped across the Channel by pipelines known generically as PLUTO.

This COSSAC plan—it was really a feasibility study—was approved at the Quebec conference in August 1943 (see QUADRANT) at which Churchill requested a 25% increase in the assault force. No firm decision on this request was made until January 1944 when, despite the acute shortage of landing craft, it was decided to expand the assault force from three divisions to eight, three of them airborne.

In February 1944SHAEF, the HQ of the Allied Expeditionary Force's Supreme Commander, General Eisenhower, was activated, and OVERLORD's land, air, and sea commanders ( Montgomery, Leigh-Mallory, and Ramsay) produced the NEPTUNE Initial Joint Plan. This incorporated the expanded assault forces, but to have the landing craft available to transport them the French Riviera landings, planned originally to coincide with NEPTUNE, and NEPTUNE itself, had to be delayed.

Timing was critical. All Allied amphibious operations in the Mediterranean had started under cover of darkness; but, because of the complexity and vastness of the landings, and because air and naval forces could only neutralize the heavily defended coastline in daylight, it was decided to assault after dawn. Other factors limited the landings to about one hour after low water and this, plus the need for the airborne troops to have a full moon, narrowed the first possible days down to 5, 6, and 7 June. The chosen day was 5 June, but the landings were delayed 24 hours because of bad weather (see also meteorological intelligence).

To guard the time and place of the landings the most stringent measures were taken to maintain security. All plans relating to them were given the classification of BIGOT and all officers involved in them were said to be BIGOTed, and were forced to follow the strictest of guidelines. Civilian travel between the UK and Eire was stopped and a coastal belt 16 km. (10 mi.) deep, stretching from the Wash to Land's End, and either side of the Firth of Forth, was closed to all but authorized travellers. Neither diplomats nor their couriers were permitted to enter or leave the country and only the Americans and the Soviets were allowed to continue to transmit signals in their diplomatic ciphers. The Polish government-in-exile also continued sending cipher signals, though neither the USA nor the USSR were told it was doing so. It was allowed to continue because the British could not break the Polish diplomatic cipher and it was thought that if they could not do so, then neither could the Germans.

The Germans were, of course, well aware that the Allies intended to invade, but deception kept them guessing as to where the landings would be, and, once they had occurred, whether they were a diversionary operation. They were also afflicted by an unsatisfactory command system (see Chart) and conflicting methods of organization. Neither the C-in-C West, Field Marshal von Rundstedt, nor the commander of Army Group B, Field Marshal Rommel, had any control over the naval and air forces in France, while the two men held differing views on how any invasion should be defeated. Rundstedt believed that nothing could prevent the Atlantic Wall defences from being pierced and that the best hope was to hold a large mobile force in reserve, positioned to strike once the Allies had landed. But Rommel and Hitler were convinced that any invasion had to be beaten on the beaches and that reserves should be positioned close to the most vulnerable places. In the event neither policy was pursued properly and in April the armoured reserves were divided between Rommel and Hitler's Armed Forces High Command, so that Rundstedt had none.

In the first six months of 1944 Rommel strongly reinforced the defences and placed obstacles such as element C on all large beaches. Extra troops were also brought in so that by the end of May Rommel's two armies (Fifteenth in northern France and Seventh in Normandy) comprised 25 static coast divisions, 16 infantry and parachute divisions, 10 armoured and mechanized divisions, and 7 reserve divisions. But the Third Air Fleet in France remained weak—only 319 of its aircraft operated on D-Day, though within a week it had been boosted to 1,000—while German naval surface forces amounted to only 4 destroyers in the Atlantic ports and 39 E-Boats between Ijmuiden and St Malo.

Much of Rommel's work to reinforce the Channel coast, and to rush reinforcements to the invasion beaches, was hampered by Leigh-Mallory's tactical air forces, and by the two strategic air forces (Bomber Command and Eighth USAAF) which the Combined Chiefs of Staff placed temporarily under Eisenhower's command. Between 1 April and 5 June 1944 more than 11,000 aircraft from these Allied air forces flew more than 200,000 sorties in support of the invasion, dropping 195,000 tons of bombs on rail and road communications, airfields, military installations, industrial targets, and coastal batteries and radar positions. Nearly 2,000 were lost, but the bombers wrought havoc with the German communications and supply routes which seriously hampered the reinforcement of those troops trying to contain the Allied bridgehead. The Allied air forces also achieved almost total air supremacy and as the historical staff of the Luftwaffe commented, ‘the outstanding factor both before and during the invasion was the overwhelming air superiority of the enemy.’

Another important factor that hampered the Germans before and after the landings was the work of the French resistance. By May 1944 it was calculated that some 100,000 Frenchmen, armed and helped by SOE and the Office of Strategic Services, were ready to take orders from the head of the Free French Forces of the Interior (see FFI), General Koenig. There were, too, some 35–45,000 armed maquis, though a quarter of these had only enough ammunition to fight for a day. Before and after D-Day special teams (see Cooney, Jedburgh and Sussex) were dropped to gain intelligence, and to support the French resistance. Sabotage was widespread: the railway system and the Germans' communication network were severely disrupted.

NEPTUNE began just after midnight on 6 June—known then and now as D-Day—when 23,400 British and US paratroopers were landed on the flanks of the invasion beaches. On the left flank 6th British Airborne Division was dropped east of the River Orne, and on the right flank 82nd and 101st US Airborne Divisions were dropped between Ste Mère Eglise, the first village in France to be liberated, and Carentan. Then, starting at 0630, the assault divisions were delivered by five naval assault forces to their beaches, which were codenamed (from west to east) UTAH, OMAHA, GOLD, JUNO, and SWORD. Each naval assault force was given the first letter of the codename of the beach on to which it was to deliver its division. There were also two additional naval forces, B and L, which were associated with landing the follow-up troops. Nearly 7,000 ships and landing craft were employed to bombard German positions, land the five Allied divisions, create the two artificial harbours which had to be towed across the English Channel, and counter any German naval attacks. Of the 1,213 naval warships involved 79% were British and Canadian, 16.5% were American, and 4% were Dutch, French, Greek, Norwegian, and Polish. Including the Allied merchant navies, 195,701 naval personnel took part. The Allied Expeditionary Air Forces also played their part, protecting the armada from air attack, bombing German defences, and creating a ‘ghost’ invasion force which deceived German radar (see electronic warfare).

Altogether 75,215 British and Canadian troops and 57,500 US troops were landed on D-Day. There were about 4,300 British and Canadian casualties, and 6,000 US ones.

NEPTUNE officially ceased on 30 June 1944, by which date 850,279 men, 148,803 vehicles, and 570,505 tons of supplies had been landed for the loss of 59 ships sunk and 110 damaged. Pressure mines (see mine warfare, 2) caused a substantial number of naval casualties, and a storm on 19 June, which wrecked one of the artificial harbours, caused many more. See also amphibious warfare and Normandy campaign.