The Map Room at Southwick House, Hampshire still hosts the original map that was used to plan the assault on D-Day (otherwise known as Operation Neptune). The map is now managed by the National Museum of the Royal Navy.

Phase 01


By June 1940, Nazi Germany and the Axis Powers had occupied most of Europe. Soon after, the Western Allies hatched a plan to land troops on the beaches of Normandy and create a beachhead from which they could open a second front to liberate the Continent. This plan was codenamed Operation Neptune, better known as... D-Day.


Landing thousands of troops on the Normandy beaches was a difficult and complex task which required planning and precise organisation. The first mission was to destroy or immobilise the German defenders and this was a job that was given to the Royal Navy.

Phase 01

Early planning

The defeat of Nazi Germany was agreed by the Western Allies as the main aim of the war by December 1941. Lieutenant-General Frederick Morgan and his team of British, American and Canadian officers submitted plans for the invasion in July 1943.

Detailed planning for a major cross-Channel amphibious operation began in late April 1942 under the codename 'Round Up'. Admiral Sir Bertram Ramsay was appointed the naval commander and although he was soon diverted to Mediterranean operations, a small staff continued to plan the necessary UK infrastructure.

The Seine Bay was chosen for the assault as early as January 1943. In May 1943, the Commander-in-Chief, Portsmouth, Admiral Sir Charles Little was appointed as the chief of the naval plan. In June 1943, the 'Rattle' conference made definite conclusions on planning and provision of equipment, including the need for artificial harbours. Ramsay resumed naval command as Allied Naval Commander Expeditionary Force (ANCXF) in October 1943 and the plans went through several iterations until the naval plan was 'frozen' on 12 May 1944.

Phase 01


The Allies needed a better understanding of the German defences before they planned the invasion. Reconnaissance of the German defences in France was carried out by a combination of gathering holiday photographs from members of the public, air reconnaissance, and specialist units like the Combined Operations Pilotage Parties (C.O.P.P.).

Phase 01

Planning Neptune

Landing thousands of troops on the Normandy beaches was a difficult and complex task that required planning and fine organisation. The first mission was to destroy or immobilise the German defenders and this was a job that was given to the navy. Large gun ships, such as the battleship HMS Rodney, and smaller rocket-armed landing craft were commissioned for destroying the German defences as well as many anti-aircraft vessels.

Phase 01


Thousands of men needed to be recruited for the operation. A special training scheme to recruit the extra officers needed for the landings was established at Lochailort in Scotland. Men were trained day and night in beaching landing craft.

Phase 01

Planning supplies

An enormous volume of ammunition was required for the naval bombardment of the German defences. Ammunition was stowed in lighters - large barges which were towed out to issuing ships either in the Solent or at sea. The bombarding ships were supplied by Ammunition Store Issuing Ships (A.S.I.S) in particular the SS Fendcris and SS Procris. A second group of ships were known as ammunition store ships and supplied the ASIS vessels.

Phase 02

D-Day: Early Phases

The plan called for most of the landing forces to pass through an area of the Channel called Area Z, 10 miles in diameter, 20 miles from the Isle of Wight. 10 mineswept channels led southwards to the assault area. Each force had a slow and a fast lane and both were timed to arrive at the same time. The bombardment forces were allocated specific targets and their main aim was to neutralise the German coastal batteries. Thereafter, their aim was to prevent the enemy from attacking the Allied flanks.

Phase 01

Postage Able

Operation Postage Able was a British series of three commando and naval beach reconnaissance operations along the Normandy coast. This work revealed crucial information about the German defences for the Allied planners.

Phase 02


Before the troops could land safely, the dangerous work of demining the Channel began. 10 flotillas of minesweepers swept the 10 channels of the spout from Area Z southwards, with each channel being marked. They then swept an area parallel to the shore for the transports to anchor and land their assault craft.

Phase 02

Operation Gambit

The job of guiding the landing craft to the beaches was given to the Submarine Service. It was called Operation Gambit.

Phase 02

Final Preparations

By 1944, over 2 million troops from over 12 countries were in Britain in preparation for the invasion. On D-Day, Allied forces consisted primarily of American, British and Canadian troops but also included Australian, Belgian, Czech, Dutch, French, Greek, New Zealand, Norwegian, Rhodesian and Polish naval, air or ground support.

On the south coast of England, troops began boarding the landing craft that would take them to France. Among them were Chinese naval officers who supported the flotilla as observers on D-Day and were paid as Royal Naval personnel. 20 of them served aboard vessels carrying out anti-submarine operations and bombardments before and during D-Day. They had been sent by China’s Generalissimo Chiang Kai-shek for training in Britain whilst the Chinese fought Japan in the Far East.

Phase 02

Airborne Landings

An important part of the D-Day plan was for Allied airborne troops to secure the flanks of the invasion area. In the east, the British 6th Airborne Division was tasked with holding ground between the Caen Canal and the River Dives so as to block German reinforcements. The most vital objective was to seize a pair of bridges over the Caen Canal and River Orne, and hold them until British forces advancing from Sword Beach arrived. Meanwhile, two American divisions were tasked with securing the western end of the Allied zone of operations.

Phase 03

D-Day: The Assault

H-Hour was set for 0600hrs on D-Day, 6 June. Each of the five assault divisions were allocated one beach with its own landing force. Landing forces took their name from the initial of the beach’s codename, such as S for Sword. Broadly speaking, the forces were subdivided with assault troops, support troops and reserves. Each landing force had a bombardment support force and a minesweeping force.

The assault fleet was divided into a Western Task Force led by Rear Admiral Allan G Kirk of the US Navy, responsible for the Utah and Omaha Beach landings, and an Eastern Task Force commanded by Rear Admiral Sir Philip Vian of the Royal Navy, responsible for the landings on Gold, Juno and Sword Beaches.

Phase 03

Naval Bombardment

Video: The Allied Naval Bombardment on the beaches begins (no sound).

On the South Coast, troops who would be involved in Operation Overlord were gathering - they began boarding the landing craft that would take them across to France. The bombarding force opened fire at 0530hrs but some of the German batteries had been moved after RAF bombing in previous weeks. However, the new battery positions were often not fully established so they were less combat ready. After the initial bombardment, ships turned to shelling targets up to 15 miles inland, spotted and called in by artillery observers ashore.

'As we approached the coast, we saw craft of various descriptions and heard the sound of bombardment. I saw a rocket-assault ship on fire, presumably having launched its rockets at the defences, heading out to sea and listing alarmingly' Major JN Rushworthy, Royal Marines

Phase 03

Eastern Sector

Video: British and Canadian troops land on Juno Beach (no sound)

The three Hampshire forces, G, J and S were due to land almost simultaneously between 0725hrs and 0745hrs. Force G reached its lowering position at 0455hrs nearly seven miles off the coast. This ensured they were out of range of enemy defences and allowed sufficient sea room for the assault craft to form up.

Over 66% of the landing craft were crewed by Royal Marines.

Phase 03

Western Sector

Forces O and U left from the areas around Weymouth and Plymouth respectively. After passing through Area Z, they began their assault on the western beaches.

Phase 03

The Beachhead

By nightfall on D-Day, the Allies were firmly ashore on all the beaches. They had occupied up to five miles inland, only half of what had been planned. Their position was not continuous but it was defensible. The Allies now had a beachhead, which was a defended position on the beaches from which they could launch an attack into the rest of France.

Phase 04

After D-Day

By midnight on 6 June, the Allies had established a beachhead five miles inland in the Seine Bay. Without access to a major port, the Admiralty implemented two innovative methods for the replenishment of fuel and munitions.

Phase 04

The Follow Up

By D+3 (3 days after D-Day), 24 convoys had sailed for the main assault and the immediate followup. Thereafter, a daily schedule of eight convoys was planned. In addition, there was a continual shuttle service of LCTs and Landing Craft (Infantry) sailing to and fro in unnumbered convoys. Southampton became the major port for the transfer of supplies to Europe.

Operation Neptune was completed on 30 June 1944 (D+24) when responsibility for the defence of shipping was transferred to the Flag Officer of the British Assault Area and the Eastern Naval Task Force was formally disbanded. On one day alone, 21 July, 75 ships were loaded for France with 10,603 tons of cargo and some 20,000 men.

Phase 04


A system of underwater pipelines known as PLUTO (generally understood to be Pipeline Under the Ocean) allowed oil to be pumped from the south coast of England to France without incurring any of the risks or capacity problems of using shipping. A flexible pipeline system, laid underwater from rolling drums, was developed from 1942 and in 1943 the Shell-Mex/BP oil storage plant at Hamble was chosen as the supply base for the project. An extended jetty was built so more craft could be moored for simultaneous loading.

Ships transported the oil from Hamble to Lepe from where it was pumped to the Isle of Wight. Pumping stations were built at Sandown on the Isle of Wight to feed Cherbourg with four pipes and from Dungeness in Kent to feed Boulogne with 16 pipes.


Phase 04

Road to Victory

The D-Day Landings marked the start of the campaign to liberate Europe and defeat Germany. German forces unconditionally surrended on 7 May 1945 and the following day Victory in Europe was declared. On 6 June 1945, the anniversary of D-Day was commemorated for the first time around Arromanches.

Phase 04

The Map

After the Second World War, the Map Room at Southwick House became an officers' mess. Several panels were added later including the original weather charts made for the D-Day operations.

Since 2017, the map has been cared for by The National Museum of the Royal Navy. To study the whole map in more detail, please switch to the artefact view at the top of the screen.

Reconnaissance: Specialist Units

A number of specialist units were involved in regularly carrying out precision surveying close to the French coast, sometimes landing to collect data and information. These units included hydrographic surveyors, swimmers and canoeists (like the Forfar Force), and the Combined Operations Pilotage Parties (C.O.P.P.). The units operated out of Warsash and Hayling Island respectively, and would report back details such as the geological make up of the various beaches, and the nature of the German coastal defences.

Training for Neptune

Several shore establishments were built from 1942, including HMS Collingwood (Fareham) to train the thousands of ratings needed for the fleet. The sheltered waters of Langstone and Chichester harbours were used for basic training whilst at HMS Northney, men learnt how to beach and unbeach their landing craft. Once they were proficient, they were sent to Scotland to train with the Army and went on to practice embarking and disembarking troops.

Reconnaissance: Operation Postage Able Phases I and II

Postage Able I was a commando undertaking to survey the area between Arromanches and La Rivière on 31 December 1943. Postage Able II was another commando beach reconnaissance operation of the Normandy coast between Pointe de Hoc and Vierville on 17 January 1944.

Reconnaissance: Operation Postage Able Phase III

Postage Able III was designed to survey the landing beaches proposed for Operation Neptune and was based on the use of the midget submarine X-20, which spent four days off the French coast to complete this task between 18 and 21 January 1944. Periscope reconnaissance of the shoreline and echo-soundings were performed during the days, and each night the X-20 approached the beach to despatch two divers, who swam ashore and collected beach samples. The divers went ashore on two nights to survey the beaches at Vierville sur Mer, Moulins St Laurent and Colleville sur Mer in what became the 'Omaha' Beach sector used by the US Army. On the third night, the divers were scheduled to go ashore off the estuary of the Orne river in what became the 'Sword' Beach area, but by this stage exhaustion (the crew and divers had been living on little more than Benzedrine tablets) and the worsening weather caused the skipper to shorten the operation and return to the X-craft base, HMS Dolphin, on 21 January.

Preparing supplies

All of these vessels required ammunition and the arrangements for supplying them were issued in a secret document. Ammunition was prepared at the Royal Naval Armament Depot Priddy's Hard, as well as other sites in the area, but Priddy's Hard was the main distribution centre for at least a year before D-Day. More than half of the 3,000-strong workforce at Priddy's Hard were women.

Operation Gambit

Two midget submarines, X-20 and X-23 were ordered to sail from HMS Dolphin at Gosport to the coast near Ouistreham on 2 June. They were initially escorted by trawlers for a third of the way then went submerged to Ouistreham at the eastern end of Sword beach. They were supposed to surface on the morning of D-Day to show lights and markers indicating the limits of the beaches and in particular where the amphibious tanks could come ashore. They silently arrived on the morning of 4 June, checked their positions and returned underwater. Just before midnight, they surfaced but had to postpone all of 5 June. The midget submarines contained five men in a cabin 5ft 8in by 5ft long. At 0445hrs on 6 June they surfaced and started flashing their signals from their 18ft masts, replacing the lights with a flag when daylight approached. Two hours later, they returned to Largs and then Dolphin.

British Airborne Landings

At around 0015hrs on 6 June, three gliders crashed only metres from the Caen Canal bridge at Bénouville, their occupants spilling out to engage the enemy. The shocked German guards were quickly overwhelmed. Two more gliders landed near to the Orne River bridge at Ranville and this too was taken virtually unopposed. The sixth glider landed in error some miles away. More paratroopers were dropped later and by the end of D-Day, the 6th Airborne Division's operations were deemed successful, having achieved all their objectives in the necessary time frame.

American Airborne Landings

Shortly after the British landings, paratroopers from the 101st and 82nd American Airborne Divisions landed in the area behind Utah beach to secure the western end of the Allied zone of operations before the amphibious landings. Due to bad weather and heavy anti-aircraft fire, many of the paratroopers were scattered but despite this they managed to secure the vital communications hub of Sainte-Mère-Église by nightfall on 6 June.

HMS Caroline and RML 497

On D-Day, HMS Caroline, based in Belfast Harbour, acted as an important communications centre for the fleet. On 3 June 1944, around 30,000 American military personnel left Belfast Lough for Utah and Omaha beaches in Normandy.   RML 497 was a motor launch which formed part of the Air Sea Rescue forces to rescue downed Allied airmen during the Normandy campaign. 'By this time, the Air Sea Rescue had been organised properly. The North Sea had been divided into areas in such a manner that if a pilot came down during daylight he would be pretty certain to be spotted by an Air Sea Rescue boat, no matter how far he drifted in the water.' Les Parkinson, Motor Mechanic on RML 497. The National Museum manages and maintains both HMS Caroline and RML 497.

The Naval Bombardment: The Air Forces

The Allies had overwhelming air superiority over Normandy by June 1944. Spotting for the ships' fire was carried out by Seafires of 808, 885 and 886 squadrons operating from Lee-on-the-Solent but RAF and USAAF forces were also in close support. 11,590 Allied aircraft flew on D-Day.

Southwick Park: Nerve Centre of D-Day

On 26 April 1944, Admiral Ramsay moved his headquarters to Southwick Park, overlooking Portsmouth Dockyard. The house there soon became a hive of activity as it was where the assault phase of Neptune was directed from by the Allied commanders. Audio: Phyllis Thomas recalls working long hours at Southwick House.

Gold Sector

After the fleet bombardment, the flood tide delayed H-Hour in Gold Sector until 0725hrs. The British chose to assemble seven miles from the coast for a shorter final run in by the assault craft. Bad weather affected their plans. Rather than launch the DD tanks in the raging current and force five winds, the craft brought them into the beach, behind the first wave of infantry. Most of the tanks became bogged down or disabled by enemy fire. They gradually cleared their way through the defences and by nightfall they had covered an area of five square miles.

Juno Sector

Task Force J carrying the Canadians offloaded them seven miles offshore and the shorter distance to the beach helped the troops. Like Gold Beach, Juno was wide enough to land two brigades side by side. The Canadian 7th Brigade landed at Courseulles at 0745hrs and the 8th Brigade at Bernieres at 0755hrs. H-Hour was delayed so that the tide would cover the rocks. However, many beach obstacles were also covered and around 30% of Juno's landing craft were damaged or destroyed. Heavy seas caused confusion. The prompt arrival of the armoured units, including the extra fire power of the DD tanks and the 'funnies' (AVRE - Armed Vehicles Royal Engineers with a large gun) helped the troops to take the beach. The Canadians moved inland and joined up with British elements on Gold Beach but a gap of two miles still separated them from Sword Beach by nightfall.   Audio: Marine Patrick Churchill discusses landing on Juno Beach.

Sword Sector

H-Hour was the same as on Gold (0725hrs). The beach was only wide enough for one brigade to disembark at a time due to the rocky shoals and the entry to the River Orne. Minesweeping had cleared the channel for the ships' approach. The bombarding force faced batteries from Merville and further to the East. 8th Brigade came ashore on schedule. Lovat's Commandos soon followed to reinforce the 6th Airborne Division at Pegasus Bridge. The strongpoint at La Breche was subdued by 1000. Free French forces assaulted Ouistreham. Frogmen and engineers had a hard time clearing obstacles and at one point the tide reduced the beach to a 10 yard strip. However, the exits were cleared and troops could land with little trouble. The armour was packed close together as there was only one usable road exit and the beach remained under fire. By late afternoon, the 185th Brigade had reached two miles short of Caen and here met heavy resistance from the German 21st Panzer division.

The German Navy on D-Day

The largest single cause of Allied shipping losses was the mine, which accounted for over 25% of the ships sunk or damaged beyond repair. The first major surface reaction on D-Day, by a force of torpedo boats (light destroyers) based at Le Havre resulted in the sinking of the Norwegian destroyer Svenner, which sunk with 33 men, including one Briton.

Omaha Sector

Minesweeping for Force O began at midnight. By 0300hrs, the transports had arrived and the unloading of the assault troops into landing craft began 11 miles off the beach. The sea was rough and several craft and DD tanks were swamped (of 32 DD tanks, 28 made the beach). The strong easterly tide carried most of the landing force to the wrong beaches and this had a disastrous effect on the assault plan. At 1000 yards, the leading craft came under intense and accurate fire. Many craft were grounded over 1000 yards offshore and troops leapt into deep water - some drowned under the weight of their heavy equipment. By midday, the German lines had been breached in four spots and troops began moving inshore around and bypassing heavily defended strongpoints. The beach was crammed with men trapped against the sea wall and the sheer weight of numbers blocked up the exits which prevented artillery and vehicles from landing. Supporting fire from the Navy destroyers which closed to 800 yards to destroy German pill boxes helped turn the tide of the battle. Follow up units were restricted to narrow, clear columns as obstacles could not be cleared quickly enough. V Corps did not have the planned tank or artillery support but managed to clear the beachhead to a mile inland by nightfall. Audio: Wren Jean Checketts recalls the reports coming into Southwick House about Omaha Beach.

Utah Sector

On Utah, the first troops reached the beach at 0630 but missed their targets due to the strong tides and high winds during their 11 mile run in. Due to the poor weather, their amphibious tanks left the craft 2000 yards closer to the beach than planned. Out of 32 DD tanks, only 28 made the beach. The first wave of LCAs (Landing Craft, Assault) each carrying 30 man assault teams was followed by a second wave of 32 craft who also had engineers and naval demolition teams to clear obstacles. Brigadier General Roosevelt realised the beach was lightly defended and ordered the advance. By the end of the day, the 4th Division had pushed 4 miles inland and made contact with the 101st Airborne Division.

Mulberry Harbours

Mulberry harbours were two temporary portable harbours developed by the British Admiralty and the War Office to provide shelter and offload a large volume of material across the Channel quickly until such time as the ports of Cherbourg and Le Havre could be captured. Mulberry harbours were built around Omaha and Gold Sectors for sheltered anchorage with unloading facilities for 6000 tons of stores and 1250 unwaterproofed vehicles a day.

Conservation of the Map

In 2024, the National Museum arranged for a Conservator to undertake consolidation of the flaking paint on the map. The map was also cleaned and here you can see an area of discolouration from nicotine staining near the Welsh coast.

Mulberry Harbours

Mulberry harbours were two temporary portable harbours developed by the British Admiralty and the War Office to provide shelter and offload a large volume of material across the Channel quickly until such time as the ports of Cherbourg and Le Havre could be captured. Mulberry harbours were built around Omaha and Gold Sectors for sheltered anchorage with unloading facilities for 6000 tons of stores and 1250 unwaterproofed vehicles a day.

Reconnaissance: Operation Postage Able Phases I and II

Postage Able I was a commando undertaking to survey the area between Arromanches and La Rivière on 31 December 1943. Postage Able II was another commando beach reconnaissance operation of the Normandy coast between Pointe de Hoc and Vierville on 17 January 1944.