U.S. Operations Plan Neptune

▪ Primary Source

      The “Neptune” Initial Joint Plan, presented in early February 1944 by the joint commanders of the Allied expeditionary forces charged with invading northwestern Europe, stipulated that the two separate armies of the invasion force (the British Second and the U.S. First) submit their own detailed plans for executing the landing in Normandy. By the end of the month, the U.S. First Army prepared Operations Plan “Neptune,” excerpts of which are reproduced below. This document was limited to outlining the first phase of the operation—establishing the beachhead on D-Day and over the following two to three weeks. In detailing the methods by which the naval, air, and ground forces would contribute to the success of the mission, it hints at the exhaustive planning that went into linking all arms and branches of the Allied forces into a combined effort to get men and matériel over the beaches and keep them there. The plan for moving the First Army beyond the beachhead was outlined later in the Joint Operations Plan for Operation Overlord.

      I. SITUATION

      1. GENERAL

      a. Object of “Neptune”. The object of “Neptune” is to secure a lodgment area on the continent from which further offensive operations can be developed. It is part of a large strategic plan designed to bring about the total defeat of Germany.

      b. Purpose of First U.S. Army Plan. The purpose of First U.S. Army Operations Plan “Neptune” is to provide a basis for planning by Task Force Commanders. The instructions contained herein will be complied with by subordinate commanders. Should modifications be found necessary or desirable in the course of planning, commanders will make appropriate requests to Commanding General, First U.S. Army.

      2. SUPPORTING NAVAL FORCES

      a. General Employment of Naval Forces.

      (1) The Western Naval Task Force will support the assault, follow-up and build-up of the United States Army.

      (2) It will transport the assault troops, their equipment and supplies from the ports of embarkation to the assault beaches in France. It will evacuate the wounded from the beaches in France to ports in the United Kingdom. It will provide the necessary surface cover and protection enroute, and in the transport and assault areas. It will (by naval gunfire) support the landings and subsequent advance inland and along the coast of the First U.S. Army, initially by fire on prearranged targets and later on call. . . .

      c. Naval Gunfire Support Plan.

      (4) The heavier gunfire support ships, 1 [battleship], 1 Monitor, and 7 cruisers, will commence firing upon coast defense batteries from H-40 minutes or earlier, if necessary, and continue until the battery has been silenced or captured.

      (5) The destroyers will be assigned to deliver close support fire on the landing beaches from about H-20 minutes until fire must be lifted for safety to troops. The targets for these destroyers will be strong points and defenses on the beaches and on the flanks of the beaches. If any coastal batteries are silenced prior to H Hour, cruiser fire will be directed on the beach defenses. . . .

      3. SUPPORTING AIR FORCES

      a. General Employment and Organization of the Air Force.

      (4) In the initial stage Air operations will be coordinated by the Allied Tactical Air Force and there will be one general air defense plan. . . .

      (6) Preliminary air operations will include:

      (a) Operations “Point Blank”.—The reduction of the German Air Force.

      (b) The attacking of a large number of rail centers to bring about a paralysis of the whole system.

      (c) Attacks on enemy supply dumps.

      (d) Between about D-3 and D Day attacks may be made on billeting areas of divisions likely to be used to counterattack during the initial stages of the assault.

      (e) Immediately before and during D Day, attacks will be necessary against command and control centers of the enemy's ground and air forces.

      (f) Attacks on enemy E boats, destroyers, and U boats in their bases.

      (g) Air mine laying operations.

      (h) Increased Anti-Surface vessel patrols, and Anti-U-Boats operations.

      (7) The Air Commander-in-Chief will control the strategic operations in the preliminary phase. . . .

      b. Preliminary Air Bombardment.

      (1) The over-riding commitment in the assault phase will be the gaining and maintaining of air superiority. Subject to this, the maximum possible effort will be made available during the period night of D-1/D Day and D Day, and subsequently as necessary for the vital tasks of assisting the Navy to neutralize the coast defenses, help the land forces in their initial occupation of the bridgehead, and delay the arrival of the enemy's immediate reserves and reinforcements. These roles will call for night and day bombing.

      (2) Attacks on enemy reinforcements will require prearranged bombing of special key points, and in addition a proportion of the bomber effort will be held in readiness to engage opportunity targets. . . .

      e. Airborne Operations.

      (1) The 101st Airborne Division under command of First U.S. Army will land on the area behind the Varreville 4299-Carentan 3984 beaches with the main object of assisting the seaborne landing. The 82nd Airborne Division will land just after the 101st Airborne Division in the First U.S. Army Zone astride the Merderet River west of St. Mere-Eglise.

      (2) The general scheme will be that pathfinder aircraft will drop key paratroop personnel at selected points during the hours of darkness to mark and prepare the Dropping Zones and Landing Zones for the dropping of the main forces, including gliders. . . .

      4. SUPPORTING GROUND TROOPS

      a. British Second Army.

      The British Second Army will attack on the left of the First U.S. Army. The initial assault will be made by three (3) divisions between Tracy-sur-Mer and Ouistreham. These divisions will capture Bayeux and Caen on D Day. The 50th Division, part of the XXX Corps, will be on the left of the First U.S. Army.

      b. Subsequent British Operations.

      Following the initial assault, the British Second Army will continue to advance in accordance with phase lines shown in Annex No. 20, protecting left flank First U.S. Army. Eventually, both the Second British Army and First Canadian Army will be employed on the left of the First U.S. Army.

      c. Diversions aimed at deceiving the enemy as to the exact time and place of our assault are being considered by higher headquarters. Commanders will be informed when definite decisions have been reached.

      d. SOE/SO Operations.

      Resistance Groups will put into effect throughout France and Belgium certain prearranged plans, including particularly attacks on enemy rail, road, and telecommunications. In addition, Resistance Groups will be called on to perform missions in strategic back areas designed to interfere with the enemy's moves to oppose the advance of the Army. Small, specially trained and equipped military units will be prepared to operate in the enemy's rear with resistance elements to carry out specific harassing and destructive missions. For SOE/SO Plan, see Annex No. 25. . . .

      II. MISSION

      6. MISSION OF FIRST U.S. ARMY

      a. Scheme of Attack.

      The First U.S. Army will launch a simultaneous assault on Beaches Utah and Omaha on D Day and H Hour; it will capture on D Day objectives as shown in Assault Plan (Annex No. 19), and thereafter will advance as rapidly as the situation permits, capturing Cherbourg with the minimum of delay and developing Vierville-sur-Mer, Colleville-sur-Mer beachhead southwards towards St. Lo in conformity with the advance of the Second British Army. The attack on Utah Beach will be made by the VII Corps with the 4th Division (Force “U”) in the initial assault, and the attack on Omaha Beach will be made by the V Corps with a composite division of the 1st and 29th Infantry Divisions (Force “O”) and the 2nd and 5th Ranger Battalions in the initial assault, and the remainder of the divisions in the immediate follow-up (Force “B”). . . . The 101st Airborne Division will begin landing in rear of Utah Beach commencing at approximately CT - 5 hrs on D Day and will assist the 4th Division in capturing its objective. The 101st Airborne Division, upon landing, becomes attached to the VII Corps. The 82nd Airborne Division will land commencing at approximately CT - 5 hrs on D Day in an area astride the Merderet River west of St. Mere-Eglise. Fifty-two (52) gliders for the 82nd and fifty-eight (58) for the 101st A/B will land at dawn on D Day. 150 gliders for the 82nd A/B will land at dusk on D Day. 100 gliders will land at dawn and 100 gliders will land at dusk on D + 1 for the 82nd A/B. Upon landing, the 82nd Airborne Division is attached to the VII Corps. . . .

      c. Employment of Units Arriving Subsequent to D Day.

      The XIX Corps will land over Omaha Beach and be employed generally on the right of the V Corps. The VIII Corps (Third U.S. Army) will arrive after D + 14 and, operating under First U.S. Army, will capture the Brittany Peninsula.

      7. TIME AND DATE

      a. D Day and H Hour.

      D Day and H Hour will be announced to Commanders shortly before embarkation of assault and follow-up forces commences. D Day will be subsequent to Y Day which has been definitely established as 31 May 1944. All references or schedules relating to “Neptune” will be made in relation to Y Day. H Hour will be shortly after daylight. . . .

      14. GENERAL

      b. Air and Coast Defense.

      Within the zone of action of First U.S. Army, all active means of air defense, including antiaircraft artillery, barrage balloons, smoke screens, and fighter aircraft, will be employed in a coordinated and complementary defense. The Commanding General, First U.S. Army, is responsible for the antiaircraft artillery defense of the vital areas, including airfields, in this zone of action. The 47th AA Brigade will provide protection for the beaches as target areas. First priority of areas to be defended will be artificial harbors, beaches, beached craft, beach exits, airfields under construction, operational airfields, and shipping lying off beaches. Second priority will be forward areas to include defiles, artillery positions, corps and division installations and troop concentrations. The fire of antiaircraft artillery weapons aboard ships in ports, artificial harbors, or anchored off beaches, will be coordinated with the shore antiaircraft defenses when such ships are included in the air defense communication system. Certain antiaircraft may be assigned a primary coast defense role. Initially, air defense operations will be coordinated by Commander, Allied Tactical Air Forces and there will be one general defense plan. Under this plan, restrictive control may be exercised over the firing of antiaircraft artillery weapons, operation of barrage balloons, searchlights, and smoke screens, but will be exercised only when necessary to safeguard or assist friendly aircraft operating over the First Army zone of action. . . .

      k. Training Exercises and Rehearsals.

      The V and VII Corps will each hold one Amphibious Training Exercise for Forces “O” and “U” in the Slapton Sands Area during March. These exercises will approximate as closely as possible the plan envisaged for “Neptune”. In addition, one dress rehearsal will be held for Forces “O”, “U” during April in the Slapton Sands Area. . . .

      24. CIVIL AFFAIRS PLAN

      a. Civil Affairs control will be through Command channels.

      b. Civil Affairs staff officers will form an integral part of the staff and Civil Affairs detachments will be assigned to subordinate units in accordance with requirements and will go forward with them. On the continent commanders will deal with local civil authorities through Civil Affairs staffs and detachments wherever practicable.

      c. The staffs will be charged with coordination of contacts with the local population, except in certain cases, those of CIC, and with operational control of the Civil Affairs detachments attached to their respective headquarters. These staffs and detachments will be responsible for local action with regard to billeting, securing warehouse space, and procurement of local vehicles, supplies, and personnel for use by the Army.

      d. Their contacts will be governed, pending political instructions to the contrary, by the principle that the commander is in full control of all Civil Affairs within the area uncovered by his troops. . . .

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