Operation Cobra was an offensive launched by the First United States Army under Lieutenant General Omar Bradley seven weeks after the D-Day landings, during the Normandy campaign of World War II. The intention was to take advantage of the distraction of the Germans by the sustained British and Canadian attacks around Caen, and thereby break through the German defenses that were penning in their forces, while the Germans were unbalanced. Once a corridor had been created, the First Army would then be able to advance into Brittany, rolling up the German flanks once free of the constraints of the bocage country. After a slow start, the offensive gathered momentum and German resistance collapsed as scattered remnants of broken units fought to escape to the Seine. Lacking the resources to cope with the situation, the German response was ineffectual and the entire Normandy front soon collapsed. Operation Cobra, together with concurrent offensives by the British Second Army and the Canadian First Army, was decisive in securing an Allied victory in the Normandy campaign.
Having been delayed several times by poor weather, Operation Cobra commenced on 25 July 1944, with a concentrated aerial bombardment from thousands of Allied aircraft. The bombardments resulted in friendly fire casualties, including Lieutenant General Lesley J. McNair who was on the front line as an observer. Supporting offensives had drawn the bulk of German armored reserves toward the British and Canadian sector and, coupled with the general lack of men and materiel available to the Germans, it was impossible for them to form successive lines of defense. Units of the U.S. VII Corps led the initial two-division assault, while other First U.S. Army corps mounted supporting attacks designed to pin German units in place. Progress was slow on the first day but opposition started to crumble once the defensive crust had been broken. By 27 July, most organized resistance had been overcome and the VII and VIII Corps advanced rapidly, isolating the Cotentin Peninsula.
By 31 July, XIX Corps had destroyed the last forces opposing the First Army, which emerged from the bocage and liberated Avranches. Reinforcements were moved west by Field Marshal Günther von Kluge and employed in various counterattacks, the largest of which, Unternehmen Lüttich (Operation Liège), was launched on 7 August between Mortain and Avranches. Although this led to the bloodiest phase of the battle, it was mounted by already exhausted and understrength units and was a costly failure. On 8 August, troops of the newly activated Third United States Army captured the city of Le Mans, formerly the German 7th Army headquarters. Operation Cobra transformed the high-intensity infantry combat of Normandy into rapid maneuver warfare and led to the creation of the Falaise pocket and the loss of the German strategic position in northwestern France.
Background
Following the successful Allied invasion of Normandy on 6 June 1944, progress inland was slow. To facilitate the Allied build-up in France and to secure room for further expansion, the deep water port of Cherbourg on the western flank of the U.S. sector and the historic town of Caen in the British and Canadian sector to the east, were early objectives. The original plan for the Normandy campaign envisioned strong offensive efforts in both sectors, in which the Second Army (Lieutenant-General Sir Miles Dempsey) would secure Caen and the area south of it and the First U.S. Army (Lieutenant General Omar Bradley) would "wheel round" to the Loire valley.
General Sir Bernard Montgomery—commanding all Allied ground forces in Normandy—intended Caen to be taken on D-Day, while Cherbourg was expected to fall 15 days later. The Second Army was to seize Caen and then form a front to the southeast, extending to Caumont-l'Éventé, to acquire airfields and protect the left flank of the First U.S. Army as it moved on Cherbourg. Possession of Caen and its surroundings—desirable for open terrain that would permit maneuver warfare—would also give the Second Army a suitable staging area for a push south to capture Falaise, which could be used as the pivot for a swing east to advance on Argentan and then the Touques River. The capture of Caen has been described by the British official historian Lionel Ellis as the most important D-Day objective assigned to the British I Corps (Lieutenant-General John Crocker). Ellis and Chester Wilmot called the Allied plan "ambitious" since the Caen sector contained the strongest defenses in Normandy.
The initial attempt by I Corps to reach the city on D-Day was blocked by elements of the 21st Panzer Division and with the Germans committing most of the reinforcements sent to meet the invasion to the defense of Caen, the Anglo-Canadian front rapidly congealed short of the Second Army's objectives. Operation Perch in the week following D-Day and Operation Epsom (26–30 June) brought some territorial gains and depleted its defenders but Caen remained in German hands until Operation Charnwood (7–9 July), when the Second Army managed to take the northern part of the city up to the River Orne in a frontal assault.
The successive Anglo-Canadian offensives around Caen kept the best of the German forces in Normandy, including most of the armor, to the eastern end of the Allied lodgement but even so the First U.S. Army made slow progress against dogged German resistance. In part, operations were slow due to the constraints of the bocage landscape of densely packed banked hedgerows, sunken lanes and small woods, for which U.S. units had not trained. With no ports in Allied hands, all reinforcement and supply had to take place over the beaches via the two Mulberry harbors and were at the mercy of the weather.
On 19 June, a severe storm descended on the English Channel, lasting for three days and causing significant delays to the Allied build-up and the cancellation of some operations. The First U.S. Army advance in the western sector was eventually halted by Bradley before the town of Saint-Lô, to concentrate on the seizure of Cherbourg. The defense of Cherbourg consisted largely of four German battlegroups formed from the remnants of units that had retreated up the Cotentin Peninsula, but the port defenses had been designed principally to meet an attack from the sea. Organized German resistance finally ended on 27 June, when the U.S. 9th Infantry Division managed to reduce the defenses of Cap de la Hague, north-west of the port. Within four days, VII Corps (Major General J. Lawton Collins) resumed the offensive toward Saint-Lô, alongside XIX Corps and VIII Corps, causing the Germans to move more armor into the U.S. sector.
Planning
The originator of the idea for Operation Cobra is disputed. According to Montgomery's official biographer, the foundation of Operation Cobra was laid on 13 June. Planning was immensely aided by detailed Ultra intelligence which supplied up-to-date decodes of communications between Oberkommando der Wehrmacht (OKW, the German armed forces high command) and Hitler's generals. Montgomery's plan at that time called for the U.S. First Army to take Saint-Lô and Coutances and then make two southward thrusts; one from Caumont toward Vire and Mortain and the other from Saint-Lô toward Villedieu and Avranches. Although pressure was to be kept up along the Cotentin Peninsula towards La Haye-du-Puits and Valognes, the capture of Cherbourg was not the priority. With the capture of Cherbourg by VII Corps on 27 June, Montgomery's initial timetable was overtaken by events and the thrust from Caumont was never adopted.
The month of July saw the Normandy front in deadlock as two German armies faced of with two Allied armies. The Germans spent the start of July in turmoil as a comprehensive reshuffling of command was underway and casualties doubled. The Wehrmacht could scarcely replace it mounting losses compared to the Allies.
Following the conclusion of Operation Charnwood and the cancellation of the First Army offensive towards Saint-Lô, Montgomery met with Bradley and Dempsey on 10 July to discuss plans for the 21st Army Group. Bradley said that progress on the western flank was very slow but that plans had been laid for another breakout attempt, codenamed Operation Cobra, to be launched by the First Army on 18 July. Montgomery approved the plan and that the strategy would remain the diversion of German attention from the First Army to the British and Canadian sector. Dempsey was instructed to "go on hitting, drawing the German strength, especially the armour, onto yourself—so as to ease the way for Brad". To accomplish this, Operation Goodwood was planned and Eisenhower ensured that both operations would have the support of the Allied strategic bombers.
On 12 July, Bradley briefed his commanders on the Cobra plan, which consisted of three phases. The main effort would be under the control of VII Corps. In the first phase, the breakthrough attack would be conducted by the 9th Infantry Division (Major General Manton S. Eddy) and the 30th Infantry Division (Major General Leland Hobbs), which would break into the German defensive zone and then hold the flanks of the penetration while the 1st Infantry Division (Major General Clarence Huebner) and 2nd Armored Division (Major General Edward H. Brooks) pushed into the depth of the position until resistance collapsed. The 1st Infantry Division "was to take Marigny, with this objective exploited by a stream of General Watson's 3rd Armored Division armor that would move south toward Coutances". The 2nd Armored Division—part of "Collins' exploitation force" of the 2nd Armored Division in the east of the VII Corps sector and the "1st Infantry Division reinforced by Combat Command B (CCB) of the 3rd Armored division in the west"—would "pass through the 30th Infantry Division sector ... and guard the overall American left flank." If VII Corps succeeded, the western German position would become untenable, permitting a relatively easy advance to the southwest end of the bocage to cut off and seize the Brittany peninsula. First Army intelligence estimated that no German counterattack would occur in the first few days after Cobra's launch and that if they did later, they would be no more than battalion-sized operations.
Cobra was to be a concentrated attack on a 6,400 m (7,000 yd) front, unlike previous U.S. broad front offensives and would have a mass of air support. Fighter-bombers would concentrate on hitting forward German defenses in a 230 m (250 yd) belt immediately south of the Saint-Lô–Periers road, while General Spaatz's heavy bombers would bomb to a depth of 2,300 m (2,500 yd) behind the German main line of resistance. It was anticipated that the physical destruction and shock value of a short, intense preliminary bombardment would greatly weaken the German defense so in addition to divisional artillery, Army- and Corps-level units would provide support, including nine heavy, five medium and seven light artillery battalions. More than a thousand divisional and corps artillery pieces were committed to the offensive and approximately 140,000 artillery rounds were allocated to the operation in VII Corps, with another 27,000 for VIII Corps.
To overcome the constraints of the bocage that had made attacks so difficult and costly for both sides, Rhino modifications were made to some M4 Sherman, M5A1 Stuart tanks and M10 tank destroyers, by fitting them with hedge-breaching 'tusks' that could force a path through hedgerows. German tanks remained restricted to the roads but U.S. armored vehicles could maneuver more freely, although the effectiveness of the devices was exaggerated. By the eve of Cobra, 60 percent of the tanks of the First Army had the rhino modification. To preserve operational security, Bradley forbade their use until Cobra was launched. In all, 1,269 M4 medium tanks, 694 M5A1 light tanks and 288 M10 tank destroyers were available.
Supporting operations
On 18 July, the British VIII and I Corps—to the east of Caen—launched Operation Goodwood. The offensive began with the largest air bombardment in support of ground forces yet, with more than 1,000 aircraft dropping 6,000 short tons (5,400 t) of high explosive and fragmentation bombs from low altitude. German positions to the east of Caen were shelled by 400 artillery pieces and many villages were reduced to rubble but German artillery further to the south, on the Bourguébus Ridge, was outside the range of the British artillery and the defenders of Cagny and Émiéville were largely unscathed by the bombardment. This contributed to the losses suffered by Second Army, which sustained over 4,800 casualties. Principally an armored offensive in order to conserve infantry manpower, between 250 and 400 British tanks were put out of action, although recent examination suggests that only 140 were completely destroyed with an additional 174 damaged. The operation remains the largest tank battle ever fought by the British Army and resulted in the expansion of the Orne bridgehead and the capture of the portion of Caen on the south bank of the Orne.
Simultaneously, the II Canadian Corps on the western flank of Goodwood began Operation Atlantic to strengthen the Allied foothold along the banks of the Orne river and take Verrières Ridge to the south of Caen. Atlantic made initial gains but ran out of steam as casualties mounted. Having cost the Canadians 1,349 men and with the heavily defended ridge firmly in German hands, Atlantic was closed down on 20 July. At Montgomery's urging, "strongly underlined in the Supreme Commander's communications to Montgomery", the II Canadian Corps commander, Lieutenant-General Guy Simonds, began a second offensive a few days later, codenamed Operation Spring. This offensive, which began the same day that Operation Cobra was launched (25 July), had the limited but important aim of tying down German units to prevent them from being transferred to the U.S. sector, although Simonds took the opportunity to make another bid for Verrières Ridge. Again the fighting for Verrières Ridge proved extremely bloody for the Canadians, with 25 July marking the costliest day for a Canadian battalion—The Black Watch (Royal Highland Regiment) of Canada—since the Dieppe Raid of 1942. A counterstroke by two German divisions pushed the Canadians back past their start lines and Simonds had to commit reinforcements to stabilize the front.