By late December 1941, the Allies had the benefit of more than a year of cross-Channel invasion planning. Following their expulsion from the Continent in early June 1940, the British had undertaken numerous studies on the subject. In early 1942, those efforts yielded Round Up, the earliest version of a cross-Channel invasion plan, and Sledgehammer, a contingency plan to land troops in France should the Soviet Union suddenly collapse. But cross-Channel initiatives were constantly interrupted by the immediacy of other pressing operations, such as the August 1942 Dieppe Raid; Operation Torch, the November 1942 landings in North Africa; and the 1943 invasions of Sicily and Italy. During this period, many different plans for invading northwestern Europe were considered, some more feasible than others. Even U.S. Army Chief of Staff General George C. Marshall and General Dwight D. Eisenhower, who in December 1943 would be selected as Supreme Allied Commander, submitted their own ideas concerning the invasion. 2
Achieving an Overall Outline
Eventually, under the guidance and direction of a group of senior British military officers known as the Combined Commanders, these efforts evolved into a number of appreciations, or studies, of the feasibility of a cross-Channel attack. One of the most important conclusions reached was the invasion should take place on the Cotentin Peninsula, in Normandy, and not the Pas de Calais, which was closer to England but more heavily defended than the peninsula. At this stage COSSAC (Chief of Staff to the Supreme Allied Commander [designate]) became involved in the planning. The forerunner of Supreme Headquarters Allied Expeditionary Force (SHAEF), COSSAC was headed by British Lieutenant General Frederick Morgan. It combined all of the earlier efforts and, because of lingering doubts, revisited the question of whether the landing site should be the Cotentin Peninsula or Pas de Calais. The invasion's top planners reached a compromise solution: Normandy's Calvados coast. The culmination of COSSAC's efforts were released in the summer of 1943 as the Overlord Outline Plan. 3
The plan called for:
a three-division assault with two follow-on divisions
a significant reduction of the Luftwaffe through an Allied air campaign of attrition—Operation Pointblank
a deception plan, which eventually evolved into Operation Fortitude, to mislead the Germans into thinking the Allies would land at the Pas de Calais.
naval gunfire support to reduce German coastal defenses.
It furthermore specifically recognized that success would require that the Allies build up their forces in France faster than the Germans could bring their armored forces, held in reserve, to bear. 4
At Churchill's insistence, Admiral Sir Bertram Ramsay was appointed Allied Naval Commander, Expeditionary Force (ANCXF)—overall naval commander of Operation Neptune—in July 1943. A consummate planner and a stickler for detail, Ramsay was involved in the preparations for almost every Royal Navy amphibious operation from Dunkirk to Sicily. His top subordinates would be the commanders of the Eastern Naval Task Force (ENTF), Royal Navy Rear Admiral Philip Vian, and the Western Naval Task Force (WNTF), U.S. Navy Rear Admiral Alan G. Kirk. Their commands, in turn, would comprise five assault forces corresponding to the invasion beaches in Normandy. 5
Despite the presence of subordinate staffs for each force, the ANCXF staff did the bulk of the naval planning at its headquarters in London. A good amount of preliminary work had been undertaken, but a number of unanswered naval operational questions remained. For example, how were the Allies to deal with the many mines the Germans had planted in the English Channel and the significant threat from the enemy's U-boats and E-boats (fast torpedo boats)? What steps were needed to protect the naval task forces from Luftwaffe attacks, and what would be the U.S and Royal navies' role in reducing German coastal defenses with gunfire? Finally, what time of day should be selected for H-hour—the precise moment of the initial landings?
Anvil and the Landing Craft Debate
One of the first challenges confronting the naval planners was determining the amount of lift, or amphibious shipping, needed to carry Allied ground forces to the shores of France. The Royal Navy calculated it could support the Overlord Outline Plan's three-division assault and two-division follow-up with the existing number of landing ships, landing craft, escorts, and other naval assets then in England. On 2 January 1944 General Bernard Law Montgomery, the hero of El Alamein and leader of the British Eighth Army in North Africa, Sicily and Italy, arrived in Britain as the commanding general, 21st Army Group and overall commander of Operation Neptune's ground forces. "Monty" quickly announced to Ramsay as well as SHAEF that the frontage of the invasion needed to be doubled to 50 miles and the size of the initial landing force increased to five assault divisions with two to follow up. This expanded Neptune's lift requirements markedly. 6
In addition to the sudden increase in the number of ships and landing craft necessary for the invasion, General Eisenhower arrived in London on 14 January intent on proceeding with a planned amphibious invasion of southern France, code-named Operation Anvil, that would occur almost simultaneously with Overlord. That meant landing craft and ships from the Mediterranean that Allied planners in England might have relied on for the newly enlarged cross-Channel invasion would not be available. 7
Between early January and mid-February, planners in England wrestled with ship capacities, ground-force footprints, and expected operational availabilities of landing craft and ships. They eventually settled on the needed number of ships and landing craft, but only after Eisenhower and Marshall agreed to postpone the landing in southern France. Montgomery, in turn, conceded to reduce the number of required vehicles and other materiel for the ground forces, and the planners sidestepped other space requirements by overloading landing craft and in some instances reassigning some cargo from assault ships to merchant shipping. 8
Naval Gunfire Support
Another important question was how much naval gunfire the invasion would require. To determine the answer, Allied planners first had to account for the priority targets the gunfire would need to neutralize—the formidable German coastal defense batteries that could range the assault beaches and shell amphibious vessels and transports. Second, lessons from the U.S. Navy and Marine Corps in the Central Pacific suggested that naval bombardments of coastal defenses needed to last days and sometimes weeks if hardened positions, such as bunkers, were to be destroyed. In fact, Rear Admiral Charles Cooke of the Chief of Naval Operations' War Plans Division gave a presentation to Prime Minister Churchill in February 1944 on the benefits of using battleships to destroy hardened defenses like pillboxes, which the U.S. Navy claimed to have effectively done earlier that month during its Kwajalein operation. 9
For the Normandy landings, naval planners ultimately decided to reject the lessons of the Pacific regarding naval gunfire support. Initial reports from the November 1943 Tarawa Atoll amphibious assault indicated that naval gunfire had been ineffective in destroying the hardened defenses on Betio Island. Unlike the amphibians of the Central Pacific, who concluded that heavier naval bombardments of longer durations were needed to fix this problem, the Normandy planners specifically decided not to attempt to destroy hardened defenses. 10
There were naturally significant differences between operating in the Pacific Ocean against an island and in the shallower, more restricted English Channel against a coastline. A preliminary study undertaken in the summer of 1943 suggested that to destroy the German coastal defenses along the invasion beaches the Allies would need more than 100 surface combatants. 11
The Graham Report, a study commissioned by the British to analyze naval gunfire-support requirements, concluded that given the resources available, the Allies were better off attempting to stun German defenders with a sudden, massive barrage of naval gunfire and then quickly assaulting the beaches before the enemy could recover. The Allies' failure to effectively destroy the Italian fortress on the island of Pantelleria, near Sicily, with an air bombardment in June 1943 suggested that demolishing hardened defenses required time and resources U.S. and British forces did not have. 12
Army planners and commanders who had witnessed the inability of artillery to destroy fixed and hardened targets during World War I were inclined to agree with those conclusions. The overriding concern that virtually eliminated the requirement for a long bombardment was the importance of tactical surprise. To spend hours, let alone days, pounding away at German coastal defenses—some of which were 11 .5 -foot-thick reinforced-concrete gun casemates—would have led to the Allies losing the race to build up forces in Normandy. 13
The ANCXF staff concluded from a study undertaken in December 1943 that the number of surface combatants necessary to stun defenders in German coastal fortifications was roughly equivalent to the number of defense batteries that could range the Normandy invasion beaches. Moreover, some of the vessels, as well as landing craft armed with artillery and rockets, could also saturate open gun emplacements and other "lighter" defenses with naval gunfire. Additional ships, primarily battleships, would be reserved to support ground forces maneuvering ashore. Finally, as a further measure the Allied air forces would bomb the beach defenses just prior to H-hour. 14
Tactical Control of Aircraft
By the time of the Tarawa assaults, the U.S. Navy and Marine Corps were singing the praises of giving centralized control of an invasion's tactical aircraft to a Navy staff located on the amphibious task force flagship. This method was very effective in the Central Pacific campaigns but was rejected by the naval planners. 15
For numerous reasons the Allied Expeditionary Air Force (AEAF) in England exercised control of all Allied tactical aircraft involved in the Normandy invasion. First, Mediterranean commanders had granted the Allied air forces tactical, land-based control during Anglo-American combined operations as far back as the North Africa campaigns and continuing through the operations in Sicily and Italy. As Supreme Commander, Mediterranean, General Eisenhower had repeatedly discussed this question with Vice Admiral H. Kent Hewitt, the commander of U.S. naval forces in northwest African waters, but decided in favor of centralized control by the Allied air forces. Since many of the same planners and commanders involved in the Mediterranean operations were now in charge of the Normandy landings, they saw no reason to change the command and control of aircraft support that had suited them in the Med. 16
Second, the missions U.S. and British tactical aircraft would fly on D-Day extended far beyond protection of the amphibious task forces, which was the U.S. Navy's primary concern. Many planes would conduct interdiction missions deep into French territory, while others would be assigned to intercept V-1 rockets and attack their launch sites (Operation Crossbow). Third, neither the U.S. Navy nor the Royal Navy had a flagship that could manage the robust communications requirements necessary to control thousands of aircraft.
A final and perhaps most important reason AEAF should control of all the tactical aircraft was that Allied planes would be taking off from hundreds of airfields in England and daily flying many different missions. It made more sense to centralize control of all of the aircraft from an Allied air forces headquarters somewhere in England. To address the navies' concern that there be a means to direct fighter cover over the naval task forces if German aircraft attacked them, ANCXF and AEAF would deploy fighter-direction tenders (FDTs)—three specially equipped LSTs, one stationed in the Western Task Force area, one in the Eastern area, and one mid-Channel—capable of communicating between the naval task force commanders and the Advanced Headquarters AEAF at Uxbridge, England, which was responsible for dispatching tactical aircraft to France. 17
Convoy and Port Operations
For D-Day and in the following days, the Allies would need to execute one of the most complex convoy, escort, and offload operations ever undertaken. This was in part because no large-scale ports were along the stretch of coastline being invaded (the capture of Cherbourg at the tip of the Carentan Peninsula was a key early objective). For offload of troops, vehicles, and cargo, landing ships and craft would need to pull onto the beach, or vessels would need to dock in artificial ports transported and towed across the Channel.
Because hundreds of supply ships of varying types would be shuttling back and forth between France and England, the Allied navies needed to track which ships were going to which destinations to ensure supplies and reinforcements arrived where needed. Naval planners devised a system for doing so based on their experiences in Operation Torch. Four letters were painted on the hull of each cargo-carrying convoy ship, designating country of departure, destination, convoy type, whether a ship had joined a convoy already bound for its destination, and if the convoy had been split into two groups. This allowed observers in the Channel to alert ports back in England of the impending arrival of certain types of ships, which in turn eased harbor traffic management. 18
The Allies designated ports from the Thames River around southern England to Bristol Channel be used specifically for the invasion build-up. Ports east of Southampton were reserved for British troops and equipment, while those west of Southampton supported U.S. troops and equipment. Southampton itself and the nearby port of Poole were joint U.S.-British support facilities. On return trips, LCTs and LSTs were ordered to use the same "hards" from which they had departed England. Merchant ships were to be preloaded before D-Day and sail directly from their ports along the Thames and Bristol Channel to their destinations in France on D+1 and D+2. 19
The planners had to coordinate precisely the process of feeding returning merchant ships into ports recently vacated by naval-assault and follow-on forces. To accomplish these tasks ANCXF created a Force Maintenance Headquarters as well as special organizations that coordinated tug operations.
When to Set H-Hour and Other Questions
The most vexing problem confronting Allied planners was what time to set H-hour. The preferences and requirements of the various types of invasion units helped shape their answer. Landing-craft coxswains desired a high or rising tide so that when they offloaded troops their vessels would not be stranded on the beach. Naval Combat Demolition Units preferred a low and falling tide so that they would have maximum time to destroy beach obstacles before they were submerged. A high tide would, and eventually did, make it close to impossible to eliminate these obstructions. Needing visibility to shell and bomb coastal defenses, navy gunners and air force bombardiers preferred an H-hour after sunrise. And finally, assault troop commanders wanted a high tide because it would leave less beach for their men to charge across while taking mortar, machine-gun, and other small-arms fire.
The eventual deciding factor that overruled all considerations was General Montgomery's requirement that the invasion have two full high tides on D-Day to ensure that LSTs could offload the maximum amount of personnel and materiel on the beaches before German armor arrived on the scene. 20
Taking all of these factors into consideration, the planners concluded that the least problematic H-hour should be a compromise—40 minutes after sunup, which also happened to be three hours after low tide. That meant that H-hour would be 0630 on the two American beaches and, because of different tidal conditions, roughly an hour later on the three British assault beaches. The LSTs would get two high tides, warships and bombers would have visibility for attacking coastal defenses, and the demolition units would have a brief window to clear paths through the beach obstacles and mines before the incoming tide covered them.
In addition to these requirements, the naval staffs had to sort out a wide range of other tactical naval issues. How were they to coordinate aircraft flying from England to serve as air spotters for naval gunfire-support ships? A significant engineering challenge was determining how to move the large artificial harbors across the Channel and where off the Normandy beaches to set them down. How to screen the naval task forces and convoys from U-boats and surface threats was another vexing problem. Finally, one of the most daunting tasks was choreographing the movement of landing craft in the assault areas. In what order should the different types of vessels hit the beaches? How fast should they proceed? How far apart should the craft and the waves of boats be spaced?
The Neptune Operational Plan
In late February, Admiral Ramsay issued the invasion's detailed naval plan, which was intended as a general guide for ANCXF's staff and task-force and assault-force commanders as they began detailed problem-solving and planning. ANCXF followed up on 10 April by releasing Neptune's final operational orders, which were divided into 22 separate sections and comprised more than 1,000 pages, including appendices and charts. The plan, which specified the movement of the assault forces and naval support vessels in minute detail, has been hailed by British military historian Correlli Barnett as a "painstaking and brilliantly successful exercise in operational predetermination." 21
Following D-Day, the U.S. Navy complained that the orders were far too rigid and did not give the task-force and assault-force commanders any room to take initiative. The Royal Navy, however, countered that for an operation as complex as Neptune, the movement of all the naval components had to be specified in ANCXF's operational orders. Failure of any of the naval forces to move exactly where they were ordered, at exactly the proper time, would have had a catastrophic effect on the invasion. Whatever the ground truth, the Operation Neptune plan nonetheless put in motion one of the largest and most complex amphibious invasions ever undertaken. 22
1. Meeting Minutes of the Combined Chiefs of Staff, 24 December 1941, Combined Chiefs of Staff Meeting Minutes, RG 216, National Archives and Records Administration, College Park, MD (hereinafter cited as NARA).
2. "Initial Planning for a Cross-Channel Attack," Records of the War Department General and Special Staffs, RG 165, NARA; Dwight D. Eisenhower, Crusade in Europe (Garden City, NY.: Doubleday, 1955), p. 47.
3. "Offensive Operations in Europe," Combined Staff Planner's Appreciation, April 3, 1942, Combined Commanders Appreciations and Reports, RG 331, NARA and Minutes of the Combined Commanders Meeting, 30 September 1942, Operational Plans and Appreciations, NARA.
4. Operation "Overlord" Outline Plan and Appreciation, 30 July 1943, Operational Plans and Appreciations, RG 331, NARA.
5. David G. Chandler and James Lawton Collins Jr., eds., The D-Day Encyclopedia (New York: Simon & Schuster, 1994), Andrew Lambert, "Bertran H. Ramsay," pp. 449-51; David Brown, "Philip Vian," pp. 584-85; John C. Reilly Jr., "Alan G. Kirk," pp. 331-32.
6. Bertram Ramsay, Year of D-Day: The 1944 Diary of Admiral Sir Bertram Ramsay , Robert W. Love and John Major, eds. (Hull, England: University of Hull Press, 1994), pp. 4-5.
7. Ibid, pp. 9-10.
8. Ibid, p. 30; Stephen Ambrose, The Supreme Commander: The War Years of General Dwight D. Eisenhower (New York: Doubleday, 1970), p. 358; Robert Coakley and Richard Leighton, Global Logistics and Strategy, 1943-5 (Washington, DC: U.S. Government Printing Office, 1968), pp. 335-6.
9. Prime Minister Winston Churchill Minute to the First Sea Lord, February 20, 1944, SHAEF Overlord-Anvil Planning Records, RG 331, NARA.
10. Gordon Harrison, Cross-Channel Attack (Washington, DC: Office of Chief of Military History, Department of the Army, 1951), pp. 192-3.
11. Ibid, p. 193.
12. "Report on Operation Neptune", vol. 1, pp. 62, 66, ANCXF Operation Neptune Reports, Joint Forces Staff College Library, Norfolk, VA (hereinafter cited as JFSCL); Bertram Ramsay, Year of D-Day , p. 51.
13. Christopher Yung, Gators of Neptune: Naval Amphibious Planning for the Normandy Invasion (Annapolis, MD: Naval Institute Press, 2006), p. 78; "Report on Operation Neptune", vol. 1, p. 66, JFSCL.
14. Annexe C, Enclosure No. 3 to ANCXF letter to Admiralty, Letter No., 128/x/0672, December 9, 1943, ANCXF Correspondence, RG 313, NARA.
15. "Amphibious Operations During the Period August to December 1943," COMINCH Report P-001, April 22, 1944, 2-13, COMINCH Reports, Second World War Published Material Shelves, JFSCL.
16. Arthur Tedder, With Prejudice: The War Memoirs of Marshal of the Royal Air Force, Lord Tedder (Boston: Little, Brown, 1967); Vincent Orange, Coningham: A Biography of Air Marshal Sir Arthur Coningham (London: Methuen: 1990); and Wesley Craven and James Cate, eds., Europe: Torch to Pointblank, August 1942 to December 1943 , vol. 2 of the Army Air Forces in World War II (Chicago: University of Chicago Press, 1949), pp. 28-9; Dwight D. Eisenhower, The Papers of Dwight David Eisenhower, vol. 3, The War Years (Baltimore, MD.: Johns Hopkins University Press, 1970), pp. 1437-38. The following senior commanders were involved in both the North African-Mediterranean landings and the Normandy invasion: General Dwight Eisenhower, Admiral Sir Bertram Ramsay, General Bernard L. Montgomery, Lieutenant General Omar Bradley, Air Marshal Sir Arthur Tedder, Air Marshal Sir Arthur Coningham, Rear Admiral Philip Vian, Rear Admiral Alan G. Kirk, Rear Admiral John L. Hall, and Rear Admiral Don P. Moon.
17. "Amphibious Operations: Invasion of Northern France, Western Task Force,"September 1944, 3-1, COMINCH Reports, JFSCL; http://www.history.navy.mil/library/online/comnaveu/comnaveu-7.htm  .
18. Christopher Yung, Gators of Neptune , p. 140.
19. Ibid; Office of Allied Naval Commander, Expeditionary Force, "Operation Neptune—Naval Orders (Short Title ON), " 10 April 1944, ANCXF Operation Neptune Naval Orders, Second World War Operational Archives Shelves, JFSCL.
20. Bernard Montgomery, Normandy to the Baltic (Federal Republic of Germany: Printing and Stationery Service, British Army of the Rhine, 1946), p. 32; see also Adrian Lewis, Omaha Beach: A Flawed Victory (Chapel Hill, NC: University of North Carolina Press, 2001), p. 150.
21. Office of Allied Naval Commander, Expeditionary Force , "Operation Neptune," 10 April 1944, JFSCL; Correlli Barnett, Engage the Enemy More Closely: The Royal Navy in the Second World War (New York: W.W. Norton, 1991), p. 797.
22. See Alan G. Kirk, "Reminiscences," Oral History Collections, Naval Historical Center, Operational Archives Branch, Washington, DC, p. 261 for the U.S. perspective on the operational plan. Also see Kenneth Edwards, Operation Neptune (London: Albatross, 1947), p. 35. For Ramsay's view, see "Report on Operation Neptune", vol. 1, 6, JFSCL.
Christopher D. Yung is the author of Gators of Neptune: Naval Amphibious Planning for the Normandy Invasion  (Annapolis, MD: Naval Institute Press, 2006). A senior research analyst at the Center for Naval Analyses, he earned his Ph.D. at the School of Advanced International Studies, Johns Hopkins University.
Operation Neptune Glossary
AEAF-Allied Expeditionary Air Force
ANCXF - Allied Naval Commander, Expeditionary Force
COSSAC-Chief of Staff, Supreme Allied Commander
SHAEF -Supreme Headquarters Allied Expeditionary Force
Landing Craft and Ships
LCA-Landing craft, assault; British version of the LCVP
LCI-Landing craft, infantry
LCI(L)-Landing craft, infantry (large)
LCM-Landing craft, mechanized
LCT -Landing craft, tank
LCT(R)-Landing craft, tank (rocket)
LCVP-Landing craft, vehicle and personnel; commonly known as a Higgins boat
LST-Landing ship, tank
Anvil-Original name for Allied invasion of southern France; later changed to Dragoon
Crossbow-Allied air operation to attack V-1 rocket launch sites
Neptune-Naval component of Overlord
Overlord-Allied invasion of northwestern Europe
Pointblank-U.S. and British bomber offensive to crush the Luftwaffe and Germany's aircraft-related industries
Torch-November 1942 Allied invasion of Northwest Africa
The Contentious Naval Commanders
The two most important personalities in the development of the Operation Neptune naval plan were Admiral Sir Bertram Ramsay, Allied Naval Commander, Expeditionary Force, and Rear Admiral Alan G. Kirk, commander, Western (U.S.) Naval Task Force. The two officers got off to a rocky start when in the fall of 1943 Ramsay informed Kirk that it was his intention to have Kirk serve as the head coordinator of U.S. naval forces strictly within a Royal Navy command structure—in other words, Kirk was expected to command nothing.
Taking advantage of his long friendship with the First Sea Lord, Admiral Sir Andrew Cunningham, the American admiral complained that he saw his role as an operational commander, directing U.S. Navy ships, landing craft, bases, and personnel. In the end, the expanding number of American naval assets supporting Neptune necessitated a command and organizational arrangement akin to Kirk's vision; however, this initial testy exchange was a harbinger of things to come.
Doctrinial differences further strained the two officers' relationship. To the U.S. Navy, the landings should be conducted in accordance with lessons learned in Central Pacific campaigns—particularly in such areas as control of aircraft and duration of bombardment of coastal defenses. Ramsay tended to dismiss such suggestions from Kirk and his staff.
The relationship soured to the point that there is some evidence suggesting Ramsay attempted to have Kirk relieved and sent back to the United States. Admiral Harold Stark, the commander of U.S. Naval Forces Europe, sent a message to Chief of Naval Operations Admiral Ernest King several weeks before the invasion, hinting that Kirk should be relieved for the sake of Anglo-American relations. King briefly considered the request before he decided it was too late to make such a significant change.
Conflicting personalities was at least partly to blame for the commanders' poor relationship. Some of Kirk's contemporaries accused him of being a "showman" and overly ambitious. Ramsay, on the other hand, has been described as very inflexible and rigid. Beyond style and temperament, most of the officers' clashes were over substantial differences of opinion on how amphibious operations should be conducted.
The tension arising from these disagreements was compounded when major setbacks occurred in the invasion preparation process. That was what happened when German E-boats penetrated Royal Navy defenses in April 1944, intercepted American LSTs conducting exercises off Slapton Sands, England, and sank two and damaged one of the ships, killing more than 700 Soldiers and Sailors. Kirk later blamed Ramsay's command-and-control arrangement in which Royal Navy Home Commands were assigned to protect the U.S. forces conducting the exercises.
In early May 1944 General Dwight D. Eisenhower got word that Kirk had insisted on a naval bombardment of E-boats in port at Cherbourg but had been turned down by Ramsay. The British commander came close to relieving Kirk for insubordination but thought the better of it and instead simply smoothed out the issue with Eisenhower.
A week later, however, the conflict between the two admirals exploded when during the final presentation of the invasion plan before King George VI, Prime Minister Winston Churchill, and Eisenhower, Kirk implied that the command arrangements were unclear. Neither Churchill nor the king was pleased with the 11th-hour criticism. Ramsay reserved the most vitriolic language for his diary, writing that Kirk "is getting me amazed by his willful stupidity."
Despite these incidents, Ramsay and Kirk managed to keep their relations positive enough to successfully plan and execute the naval portion of the Normandy invasion. Following the operation, the two actually got along quite well, cooperating as the Allies advanced toward Germany. When Ramsay tragically died in a January 1945 plane crash, Kirk was temporarily made Allied Naval Commander, Expeditionary Force.
-Christopher D. Yung