The Normandy Landings were the first operations of the Allied invasion of Normandy, also known as Operation Neptune and Operation Overlord, during World War II.
The landings began on June 6, 1944 (D-Day), at 6:30 British Double Summer Time (H-Hour). In planning, D-Day was the term used for the day of actual landing, which was dependent on final approval.
The assault was conducted in two phases: an air assault landing of American, British and Canadian airborne troops shortly after midnight, and an amphibious landing of Allied infantry and armoured divisions on the coast of France starting at 6:30.
The invasion required the transport of soldiers and materiel from the United Kingdom by troop carrying aircraft and ships, the assault landings, air support, naval interdiction of the English Channel and naval fire-support. There were also subsidiary 'attacks' mounted under the codenames Operation Glimmer and Operation Taxable to distract the Kriegsmarine and the German army from the real landing areas. The operation was the largest single-day amphibious invasion of all time, with 160,000 troops landing on June 6, 1944. 195,700 Allied naval and merchant navy personnel in over 5,000 ships were involved.

The landings took place along a 50-mile (80 km) stretch of the Normandy coast divided into five sectors: Utah, Omaha, Gold, Juno and Sword. The Allies had previously invaded mainland Europe September 3, 1943 with the landings in Italy.

Naval activity

Large landing craft convoy crosses the English Channel on 6 June 1944.

The Invasion Fleet was drawn from 8 different navies, comprising 6,939 vessels: 1,213 warships, 4,126 transport vessels (landing ships and landing craft), and 736 ancillary craft and 864 merchant vessels.

The overall commander of the Allied Naval Expeditionary Force, providing close protection and bombardment at the beaches, was Admiral Sir Bertram Ramsay who had been responsible for the planning of the invasion of North Africa in 1942 and one of the two fleets carrying troops for the invasion of Sicily in the following year. The Allied Naval Expeditionary Force was divided into two Naval Task Forces: Western (Rear-Admiral Alan G Kirk) and Eastern (Rear-Admiral Sir Philip Vian – another veteran of the Italian landings).

The warships provided cover for the transports against the enemy whether in the form of surface warships, submarines or as an aerial attack and gave support to the landings through shore bombardment. These ships included the Allied Task Force "O". A small part of the naval operation was Operation Gambit, when British midget submarines supplied navigation beacons to guide landing craft.

Coordination with the French Resistance

The various factions and circuits of the French Resistance were included in the plan for Overlord. Through a London-based headquarters which supposedly embraced all resistance groups, État-major des Forces Françaises de l'Intérieur (EMFFI), the British Special Operations Executive orchestrated a massive campaign of sabotage tasking the various Groups with attacking railway lines, ambushing roads, or destroying telephone exchanges or electrical substations. The resistance was alerted to carry out these tasks by means of the messages personnels, transmitted by the BBC in its French service from London. Several hundred of these were regularly transmitted, masking the few of them that were really significant.

Among the stream of apparently meaningless messages broadcast by the BBC at 21:00 CET on 5 June, were coded instructions such as Les carottes sont cuites ("The carrots are cooked") and Les dés sont jetés ("The dice have been thrown").

One famous pair of these messages is often mistakenly stated to be a general call to arms by the Resistance. A few days before D-Day, the (slightly misquoted) first line of Verlaine's poem, Chanson d'Automne, was transmitted. "Les sanglots longs des violons de l'automne" (Long sobs of autumn violins) alerted the resistance of the Ventriloquist network in the Orléans region to attack rail targets within the next few days. The second line, "Bercent mon coeur d'une langueur monotone" ("soothe my heart with a monotonous languor"), transmitted late on 5 June, meant that the attack was to be mounted immediately.

Josef Götz, the head of the signals section of the German intelligence service (the SD) in Paris, had discovered the meaning of the second line of Verlaine's poem, and no fewer than fourteen other executive orders they heard late on 5 June. His section rightly interpreted them to mean that invasion was imminent or underway, and they alerted their superiors and all Army commanders in France. However, they had issued a similar warning a month before, when the Allies had begun invasion preparations and alerted the Resistance, but then stood down because of a forecast of bad weather. The SD having given this false alarm, their genuine alarm was ignored or treated as merely routine. Fifteenth Army HQ passed the information on to its units; Seventh Army ignored it.

In addition to the tasks given to the Resistance as part of the invasion effort, the Special Operations Executive planned to reinforce the Resistance with three-man liaison parties, under Operation Jedburgh. The Jedburgh parties would coordinate and arrange supply drops to the Maquis groups in the German rear areas. Also operating far behind German lines and frequently working closely with the Resistance, although not under SOE, were larger parties from the British, French and Belgian units of the Special Air Service brigade.