Operation Cobra

Operation Cobra was the codename for the World War II operation planned by United States Army General Omar Bradley to break out from the Normandy area after the previous month's D-Day landings. Cobra was a great success that transformed the high-intensity infantry combat of Normandy into the highly mechanized race across France. It led directly to the creation of the Falaise pocket and the loss of the German position in northwestern France.

Background Information

The original planning for the Normandy campaign, once the initial D-Day invasion was successful, envisioned a rapid Allied build-up of forces in a steadily-expanding beachhead. Specific objectives such as towns, ports and airfields served as guidelines to operations. Eventually the Allies sought a mobile battle in which their advantages in numbers, tactical air power, armor, mechanized infantry and logistics would be brought to bear. They wished to avoid a slow, World War I-style stalemate or near-stalemate, though it was recognised that the battle would be at least partly attritional, and the original planned length of the battle was ninety days.

A critical success factor for the Allies, once a landing had been successful, was building up their highly mechanized forces in the battle area faster than the Germans. The Allies had to build up forces quickly, at the same time that they prevented the Germans from doing the same.

To prevent additional German forces from entering the battle area, Allied tactical air forces attempted to isolate the rail and road network of northern France. This effort was highly successful; German units in Normandy suffered from severe personnel and supply shortages, and new units could be fed into the battle only very slowly. Road usage during the day became suicidal for the Germans.

The other half of the equation - building up Allied forces on the continent - was also succeeding. Allied forces were growing faster than their opponents, but by July this growth was constrained by the Allied failure to "peg out claims well inland" in General Montgomery's words. The beachhead was crowded; the number of airfields in Allied hands was far fewer than planned; Caen (a D-Day objective) had not been taken; no major operating port was yet in Allied hands. In general, progress was being measured in yards rather than miles. The battle for Normandy had devolved into a series of small-unit actions in which Allied Infantry units, supported with hurricanes of artillery fire, slowly ground into the German defenses. For example, between July 2 and July 14, the U.S. VIII Corps took over 10,000 casualties while advancing only 12,000 yards. By July 25 (D+49, the start date of Cobra) the Allies had only reached the D+5 phase line; that is, they held positions they expected to have on June 11, 5 days after D-Day.

This led to frustration at the top Allied command levels. Allied Infantry losses were high, major mechanized units were not in the battle, close air support was difficult because the fighting was at such close range. The Allied commanders could not bring their advantages to bear on the battle, and the fear of another stalemate seemed to be close to reality.

This highlighted a failure of Allied pre-invasion planning. The Allies were so focused on the immense problems of the invasion itself that they failed to adequately plan for the campaign in the beachhead. Particularly on the US First Army front in the west, the tactical problems of the bocage country had not been anticipated.

On the German side, the buildup rate was the critical factor that could not be mastered. Time was not on their side.

On the tactical level, German defensive efforts were generally successful; they gave ground slowly and inflicted heavy casualties doing so. The bocage terrain in the west aided them. In the more open terrain in the east, the line had to be held by high quality mechanized units such as the 9th, 10th and 12th Waffen-SS Divisions, all their heavy tank battalions and other Panzer and Panzergrenadier units.

In the west, facing the U.S. First Army, the Germans had only a few mechanized units; the elite Panzer Lehr, 2nd SS Panzer and 17th SS Panzergrenadier divisions, with elements of the 2nd Panzer Division. Most of the line was held by virtually immobile infantry. Only two complete infantry divisions (one of them a parachute division) were in the line facing the Americans. Most of the German infantry were in battlegroups formed from the remnants of divisions almost destroyed by the previous seven weeks' fighting, or detached regiments pushed into the line to plug gaps.

On the strategic level, the Germans were playing a game they knew they would lose. By 1944 the doctrine of virtually all combatants dictated that defensive lines be held by infantry divisions. The few mechanized units should have been held in reserve behind the front as a counterattack force. The failure of German logistics to provide infantry Divisions to the front forced this strategy of using up their mechanized units in a defensive attrition battle. The complete failure of the German air force to contest Allied air supremacy meant that German units could not conduct the sort of highly mobile, fluid battle at which they excelled. Finally, the astonishing willingness of the German high command to believe in the Allied deception plan (Operation Fortitude) kept substantial German units in the Fifteenth Army sector far from the battle area.

Planning

The Allied ground forces commander was British General Bernard Montgomery. Under him he had American armies in the western part of the theater and British and Canadian in the east. Montgomery's original plan for the Normandy campaign envisioned strong offensive efforts both in the eastern and western sectors, ultimately resulting in United States forces on the west of the theater 'wheeling round' to the Loire. Over a period of several weeks, the US 1st Army commander, General Omar Bradley worked on a breakthrough plan, probably being advised by his friend tank warfare expert George S. Patton. On July 10, 1944, Bradley revealed these plans to the 21st Army Group commander, British General Bernard Montgomery (his immediate superior), and to British 2nd Army commander General Miles Dempsey (his counterpart). Montgomery instructed Dempsey to supply the supporting attacks for the American advance in this operation up to Caen by attracting as much of the German forces as possible "to ease the way for Brad". This led, in part, to Operation Goodwood which was also approved by Montgomery that day. The Supreme Commander, Eisenhower, ensured that the Allied air forces would support the attack with tactical forces as well as medium and heavy bomber units. The air commanders were reluctant to use their bombers in the tactical battle, believing both that they were unsuited to the role and that they would be better employed in their intended strategic role. Nevertheless, they participated in several 'carpet bombing' operations in Normandy on July 7 (Operation Charnwood), July 18th (Operation Goodwood) and July 24-25th (Cobra).

On July 12th, Bradley briefed his subordinate commanders. The Cobra plan had three phases. The first was for VII Corps to punch a narrow hole in the German front; second, the breakthrough Divisions would form strong 'shoulders' on either side of the breakthrough, and a three-division exploitation force would push through the gap. Meanwhile, the VIII Corps and XIX Corps would conduct local attacks to prevent German formations in their sectors from reinforcing the breakthrough area. If the first two phases were successful, German resistance on the VIII Corps front would be untenable and the entire Cotentin peninsula would be taken. General J. Lawton Collins, the VII Corps commander, suggested slight modifications to the plan, aiming the breakthrough units slightly more south. If the breakthrough were successful, Collins' modification enabled the possibility of a faster exploitation into Brittany, seizing the Atlantic ports there. The original plan did not envision the wholesale collapse of the German front in Normandy, merely a major expansion of the bridgehead, transition to more mobile warfare beyond the bocage country, and possible seizure of major ports.

The attack would be preceded by a massive bombing of the attack sector by medium and heavy bombers. It was expected that the combination of physical destruction and shock value in this short, intense bombardment would greatly weaken the German defense. Infantry units would then attack and penetrate into the German position until resistance weakened; at the critical point when resistance was collapsing in the immediate area, the exploitation force would be unleashed. Because the air strike was such a critical component of the plan, and the aircrew were dependent on good weather to hit the target, Air Chief Marshal Leigh-Mallory had responsibility to set the time of the attack.

Key units conducting the breakthrough were the US VII Corps with the 4th, 9th, and 30th infantry divisions. The exploitation force consisted of the 1st Infantry Division, the 2nd, and 3rd Armored Divisions. The 1st Infantry Division was temporarily motorized for the operation with trucks supplied by First Army quartermaster truck companies.

The U.S. VIII Corps (General Troy Middleton) had the 8th, 79th, 83rd and 90th Infantry Divisions in the assault and the 4th Armored Division in reserve.

Over 1,300 M4 medium tanks, 690 M5A1 light tanks, and 280 M10 tank destroyers were available in these units, along with hundreds of tubes of divisional and corps artillery. Approximately 140,000 rounds of artillery ammunition of all calibers was allocated to the operation. The VII Corps attack front was only 7,000 yards wide.

The Effects of Operation Goodwood

Goodwood was launched on July 18. The tactic of using heavy bombers as a form of artillery preparation was used, as at Cassino several months before. Unlike Cobra, however, Goodwood relied on a massed tank attack in the offensive rather than breaching the enemy front with infantry. Goodwood was costly - over 400 Shermans were destroyed in the operation, but secured Caen and caused the Germans to commit most of their armor to the eastern part of the theater, so that one and a half Panzer divisions faced the American armies against six and a half further east, far away from the intended attack frontage for Cobra. The Americans correctly estimated that no German counterattack would occur in the first few days after the Cobra attack, and that if attacks occurred after that date they would consist of no more than battalion-sized operations.

Pre-Attack Phase

In the days leading up to the attack, units of the US VII and VIII Corps secured jumping-off positions, at heavy cost in infantry casualties. The mission was to secure positions that were both good tactically as jumping-off points and that were easy to identify from the air. The line chosen was the Saint-Lô-Periers road.

The air commanders recommended a 3,000 yard distance between the bombing target and any friendly forces. Because the cost of these limited pre-Cobra attacks was so high, Bradley was reluctant to give up too much of the hard-won ground and wanted to withdraw only 800 yards. In the end, the front-line Infantry positions were withdrawn 1200 to 1400 yards back from the bombing zone to provide some measure of safety. Major units moved back one hour prior to the air strike, leaving observation posts behind until 20 minutes before the strike.

Initial Attack July 24-27

The date for the attack was originally set for July 18. However, poor weather delayed the attack several times, and Montgomery had told Bradley that he need not rush the operation. The date was eventually finalized for July 24. However, poor weather on that day forced Leigh-Mallory to postpone for 24 hours. Some heavy bombers from the Eighth Air Force did not get the recall order and proceeded with their mission. About 335 B-17s, some hindered by poor visibility, dropped 685 tons of bombs. Some of the bombs fell on US positions, despite the planning done to prevent just such an occurrence. Bradley had specifically requested that the aircraft approach the target area by flying parallel to the front in order to minimize the risk of friendly fire. Although he believed the air commanders had committed to the parallel route, in fact only the fighter-bombers of the Ninth Air Force approached the target parallel to the front. The bomber units had made no such agreement and approached perpendicular to the front line. The 'short' bomb drops thus fell on the very units that were expected to lead the assault.

Over 100 US soldiers were killed and approximately 500 were wounded. One unit, 1st Battalion, 120th Infantry Regiment, from the 30th Infantry Division, suffered 25 soldiers killed and 131 wounded. Perhaps the most notable soldier to die was General Lesley J. McNair.

Some consideration was given to altering or cancelling the attack, since it was presumed that the element of surprise had been lost. However, Bradley elected to go ahead. In hindsight his decision was correct; the Germans did nothing to reinforce their defenses in the 24 hours they had prior to the actual attack on July 25. They believed an actual attack attempt had been made but that it had been stopped by their artillery fire. Indeed, elements of the Panzer Lehr Division shifted slightly southward into the target area. Elements of the 2nd Panzer Division were pulled back towards the British sector in the east.

On the morning of July 25, visibility was good and the attack went ahead at 9:40am. Medium and heavy bombers dropped over 3300 tons of high explosive on the target area. Once again, bombs fell on US as well as German positions. US ground casualties on the 25th due to bombing were 111 killed and 490 wounded. Several factors contributed to the bombing errors, including the small size of the target, and the fact that wind blew smoke from the bombs towards the US positions. Some bomber crews bombed into the smoke rather than clearly identfying their targets. Given the technology available it is difficult to see how these errors could have been avoided. The friendly fire casualties that resulted were probably lower than the casualties that would have resulted from enemy fire had the bombers not been used.

The assault units recovered rapidly from the bombing. Despite heavy casualties in some units, only one battalion needed to be replaced; every other unit attacked that morning. Some units were delayed but the attack commenced by 11am.

German units were devastated by the storm of bombs. The elite Panzer Lehr Division was rendered completely ineffective by the bombing. Tanks were overturned, positions were destroyed and surviving personnel were often stunned into incoherence. Command and control largely broke down and two-thirds of the division's personnel were casualties.

The initial Infantry attack went slowly. To some extent this may have been due to the fact that units had gotten used to very slow, cautious movement through heavily defended bocage fields. Initial German resistance, while weak, was not non-existent. However, the attack gained momentum as the thin crust of the German position gave way with nothing behind it. The first day's advance of 4,000 yards, at a cost of over 1,000 casualties, was followed on the 26th by an 8,000 yard advance. Clearly, the German front was giving way.

Breakthrough and Breakout July 27-August 4

Collins gambled that a breakthrough was imminent and committed elements of all three exploitation Divisions on the morning of the 26th. This was a critical decision. Committing the exploitation units too early, before the German front was broken, would result in crowded units jamming up the attack sectors and exhausting some of their strength. On the other hand, waiting too long might result in a slower-than-necessary advance, allowing the Germans more time to shore up defenses or mount a coordinated counterattck. Thus the decision on the 26th required a good 'feel' for the battle.

By the 27th the full weight of all three Divisions was committed and the VII Corps front essentially broke open; US mechanized units were advancing at will against scattered resistance. The VIII Corps front also began to collapse as German units fell back to avoid being cut off. By the 28th Collins's judgement was vindicated as the US VIII Corps gained 12 miles and the 4th Armored Division took Coutances, a major road junction well beyond the Germans' tactical zone. At this point the VIII Corps joined the exploitation under Patton's "guidance" (the Third Army was not yet operational). By July 30 the 4th Armored Division captured Avranches, cutting off the base of the Cotentin peninsula. Meanwhile, Canadian II Corps was attacking in the east to pin German units in place. By this time there was no coherent German front facing the 1st Army. Advance units were essentially penetrating into undefended territory. By August 4th, four Divisions of the 3rd Army had advanced beyond Avranches. The bocage was left behind as the mobility of the US forces dictated the pace and direction of the battle.

On August 4th Montgomery (the overall Allied ground commander) ordered a major change in the pre-invasion plan. Instead of concentrating the US Third Army on Brittany in an effort to open up the ports there, in view of the German collapse most of the 3rd Army was sent east. Meanwhile 1st Army also drove east, and the British 2nd Army and Canadian 1st Army continued attacking east and south in an effort to encircle the remnants of the German Army. The race for the Falaise Gap and the dash across France had begun.

Effects

Cobra was a transforming operation, effectively ending the Normandy campaign and opening up the dash across France which continued until mid-September 1944. The Allied advance was finally ended not by German resistance, but by lack of supply. Allied units, victims of their own success, outran their logistics.

Ironically, the VIII Corps failed in its task of capturing the major Breton ports. Brest held out until September 1944, and Lorient remained in German hands until May 1945. But by August, with Marseille captured intact, this did not matter very much, as recognized in Montgomery's August 4th decision.

The effects of the operation were much greater than anticipated; in Bradley's words, Cobra "had struck a more deadly blow than any of us dared imagine". It is a tribute to the flexibility and extreme mobility of the Allied armies that they were able to sustain the advance for as long and as far as they did.

At noon on August 1st, the US 3rd Army was activated, taking control of the VIII Corps as planned prior to the invasion. Also at noon, the US 12th Army Group was activated, with General Bradley commanding. Command of the US 1st Army passed to General Courtney Hodges.

As the German front in Normandy collapsed, German units fled towards the east by any means they could find. Allied air power was again decisive; by interdicting roads, bridges and railways they severely reduced the rate at which the Germans could move. Major units were trapped in the Falaise pocket.

The defeat inflicted on the Germans was one of the greatest of WW2. Losses amounted to over 400,000 men, 1,500 tanks and Self-propelled guns, with 25 Divisions essentially destroyed. Losses during the breakout stage were actually much higher than in the more static battles that preceded it; for example, the loss rate of German tanks skyrocketed in August compared to June or July. German Panzer Divisions arrived on the German frontier exhausted and with no tanks.

By August 25 all four Allied Armies (1st Canadian, 2nd British, 1st US, and 3rd US) involved in the Normandy campaign were on the river Seine.

The sense of impending stalemate in the Allied high command was replaced by the euphoria of victory. To some extent both sides believed the war was as good as over. The Allies followed up the dash across France with the shortsighted decisions to forgo clearing Antwerp's approaches, launching Operation Market-Garden instead. The new German commander in the west, Gerd von Rundstedt, suggested to his superiors that the best course of action was to "make peace, you fools".

See also

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