Unlike 1914, no great demonstrations of frenzied enthusiasm greeted the outbreak of war in September 1939. Instead, silent resignation prevailed in London, Paris, and even Berlin where American foreign correspondent William L. Shirer observed a mixture of apathy, astonishment, and depression on the faces of German civilians in the streets. The specter of the hideous bloodbath of World War I still loomed over the continent. Britain and France were slow to honor their commitments to Poland. The British did not declare war until 11 A.M. on September 3 when their ultimatum demanding the evacuation of German troops from Poland expired. The French did not follow suit until another six hours had elapsed. In his speech to Parliament that day, Chamberlain glumly declared, "Everything I have worked for, everything I have hoped for, everything I have believed in has crashed in ruins." There was even less reason for jubilation in Poland where the Poles faced the full brunt of the German attack completely alone.
DIFFERING APPROACHES TO WAR
During the opening period of World War II, from September 1939 to November 1941, Germany won a series of spectacular victories and conquered much of Europe. These successes stunned the world and gave the illusion of overwhelming strength. The Germans failed only in their attempt to crush Britain in 1940, but this defeat came in the air. They remained invincible on land.
Despite appearances, Germany's triumphs were not due to overwhelming strength. Hitler's army was formidable, but considering his ambitious war aims, it was not enormously large. Much of its equipment, including tanks, was not of the highest quality and not especially plentiful. Ironically, the Germans, who revolutionized warfare through mechanization during the 1930s, were short of motorized transport. Only a few of their infantry divisions were motorized. They also faced a serious shortage of trucks for supply purposes, and the mass of their army depended on horse-drawn vehicles to transport supplies. The actual keys to Hitler's success during the first two years of the war were the ways in which German leaders used their forces and took advantage of their opponents' mistakes.
Germany's approach to war was in large part predicated on Hitler's intention of dominating Europe and creating Lebensraum. He could accomplish this only by taking the offensive. But despite Hitler's dedication to offensive warfare, most German generals in the period between the wars were expected to fight the next conflict as they had waged World War I - with mass infantry attacks. They were by no means convinced that the tank and the airplane were the weapons of the future.
During the interwar years, most French and British generals were also conservative and unimaginative in their outlook, but unlike the Germans, they were committed to defense and, in particular, fixed fortifications. They had learned what seemed to be the major lesson of World War I - the fact that victory had been won in large part by defensive firepower. Indeed, they had learned it too well.
Ironically, the French had been enthusiastic advocates of offensive warfare before and during World War I. The more optimistic of them believed that fighting spirit was the most important factor in war and that an army that possessed sufficient spirit could defeat any defensive force, no matter how powerful. The French put this suicidal doctrine into use during World War I and tried repeatedly to break the stalemate by means of mass attacks. Each time, they failed while suffering huge casualties. This experience led to a revulsion of this type of warfare among postwar French leaders, especially Marshal Henri Petain, who had opposed the prevailing offensive creed even before 1914 and commanded the French forces that stopped Germany's repeated attacks against the fortress city of Verdun in 1916. In the postwar era, he continued to champion defensive warfare. British military leaders shared the French devotion to the defense. They also had undertaken massive offenses during World War I that had resulted in meager gains at a terrible price in lives.
But there was one lesson of World War I that most French and British generals had not learned - even though the defense had been supreme during most of the conflict, it was offensive power that eventually won the war. The Germans had failed to stop the Allied offensive during the summer and fall of 1918 and had fallen back steadily, although they had prevented a breakthrough. The Allies had employed large numbers of tanks in this operation. Unfortunately, these armored vehicles, ponderous and slow, had suffered heavy losses, convincing many French and British leaders that the tank would never be a decisive weapon.
Not all French and British military men were wedded to static defensive warfare in the postwar period, however. In France, General J. B. E. Estienne, the creator and leader of the French World War I tank force, believed that the key to the next war would be fast-striking offensive operations featuring large tank formations supported by aircraft. Estienne influenced a young colonel, Charles de Gaulle, who expounded similar views in a book he published in 1934. The politician Paul Reynaud shared their belief in the importance of mobile offensive warfare. Unfortunately, Estienne, de Gaulle, and Reynaud won few followers, and the static defensive mentality remained dominant. In Britain, General J. F. C. Fuller, who had served as chief of staff of the Royal Tank Corps in 1918, insisted that the tank, operating in large formations, was the weapon of the future. His most important convert was B. H. Liddell Hart, an infantry captain whose army career had ended when he was gassed during the Battle of the Somme. Liddell Hart developed the "expanding torrent" theory of deep, swift penetration by armored units as the key to breaking a static defensive line. But he was also a strong believer in defense and contended that powerful tank forces should be used in a defensive role to counterattack enemy offensive formations. Fuller and Liddell Hart failed to convince Britain's senior military leaders of the crucial role of armor, but Liddell Hart's views on the importance of defense served to reinforce the British defensive bias.
Ironically, it was the Germans who learned from the Western advocates of armored warfare. They had been slow to appreciate the value of the tank in World War I, but during the 1930s they created large armored (panzer) formations, which France and Britain ignored. The man most responsible for this transformation was Heinz Guderian, a relatively junior officer who did not become a general until 1938. Guderian had witnessed the appalling slaughter at Verdun, which convinced him that Germany must avoid the horrors of such static warfare in the future. During the 1920s, he fell under the influence of British advocates of armored warfare, especially Liddell Hart. Guderian concluded that powerful concentrations of fast-striking, well-armored, and heavily armed tanks, closely supported by aircraft and other motorized troops, would determine the outcome of the next conflict. Guderian found it difficult to overcome the resistance of the more conservative senior generals, but he did win Hitler's support as early as 1933. He published a book in 1937 that explained his theory of armored warfare and presented what amounted to a blueprint for the future Blitzkrieg (lightning war). But Guderian was not alone. General von Fritsch, the former army commander-in-chief, and General Beck, the erstwhile chief of staff of the Army High Command, had developed the concept of "combined arms," which was crucial to the success of the German Blitzkrieg. This concept would ultimately form the key component of the Allied success later in the war.
The intent of the Blitzkrieg was to gain victory as quickly, as decisively, and with as few German casualties as possible. To accomplish this, powerful panzer forces would smash through opposing border defenses and encircle large concentrations of enemy troops. The panzer divisions themselves were balanced formations of all arms - tanks, mechanized infantry in armored halftracks, and mobile artillery. "Motorized infantry" traveling in trucks, would follow behind the armor and consolidate the initial gains while the tanks dashed deeper into the interior. Next, the traditional mass of infantry, marching on foot, would relieve the motorized infantry, allowing it to keep pace with the panzers. Meanwhile, the Luftwaffe would destroy the enemy air force, ideally catching many planes on the ground. Once they had accomplished this, German aircraft would attack enemy communications and troop formations. Tanks, motorized infantry, and airpower would all work in harmony to crush the enemy.
But while the Germans staked their future on the Blitzkrieg, the French carried their defensive doctrine to its ultimate manifestation, the construction of the Maginot line, the greatest system of fixed fortifications ever built. It consisted of massive concrete and steel forts housing guns of tremendous range and power, casements and pillboxes containing smaller guns, and shell and bombproof underground facilities. Although the line was incredibly strong, it had one glaring weakness: it extended only from the Swiss frontier to a point just beyond the convergence of the borders of France, Luxembourg, and Belgium. Unfortunately, the likely route for a German invasion was through Belgium to the northwest of the Maginot line. This would enable the enemy to outflank its powerful fortifications.
Several factors contributed to the French failure to continue the line along the Belgian border to the sea. Such an extension would have been extremely expensive and would have run through heavily industrialized urban centers. The high water table in the extreme western portion of the border area also posed problems for underground construction. And France was concerned that the Belgians might consider the extension of the line an indication that the French would not aid their country against a German invasion but would merely wait behind their defenses. Finally, the French visualized the Maginot line as only a partial defense. In case of a German attack by way of Belgium, they intended to send troops to aid the Belgians. They hoped that these forces, anchored on the Maginot line to the south, would be sufficient to stop a German offensive before it reached French soil. By pursuing such a defensive strategy, France hoped to fight a war of "limited liability" and avoid a repetition of the horrible casualties of World War I.
Britain, too, had opted for a war of limited liability, to an even greater degree than France. The British armed forces clearly reflected this decision. As an island power, Britain's first line of defense was the Royal Navy, still by far the largest in Europe. The Royal Air Force received second priority but only slowly increased in strength during the 1930s. The army came in a poor third, even after the introduction of conscription shortly before the outbreak of war. Although Britain sent an expeditionary force to France in the fall of 1939, it numbered only 250,000 men and contained just one armored division.
Despite his aggressive foreign policy and determination to take the offensive, Hitler actually had also committed Germany to a war of limited liability. He was confident that he would gain victory through a series of swift, decisive Blitzkrieg offensives that would not require full mobilization of the economy. Contrary to the view that prevailed in Britain and France, the Fuhrer had not carried out a sweeping reorganization of the German economy; in reality, much of German industry still concentrated on the production of consumer goods.
Hitler had chosen a policy of rearmament "in breadth" intended to provide the armed forces with sufficient weapons to enable them to win a series of lightning campaigns. He did not anticipate a long war and, thus, did not favor an intense mobilization of the economy to provide rearmament "in depth." Such an approach would have concentrated first on expansion of Germany's heavy industry - a vast increase in steel production and construction of additional facilities to enable the manufacture of huge quantities of war material. A policy of this type would have necessitated postponing war until at least 1943 and would have assumed a lengthy conflict.
STRENGTHS AND WEAKNESSES
In 1936, Hitler established the Four-Year Plan, under Goering's leadership, aimed at making Germany as self-sufficient as possible and ready for war within four years. The plan had only indifferent success. It did not expand German industry; it merely brought existing production facilities up to full capacity. Hitler and Goering hoped to make Germany independent in materials that the nation could produce. This would enable them to conserve foreign currency reserves for the purchase of food and raw materials that could not be produced domestically. The Four-Year Plan emphasized production of synthetic materials. Goering projected that by 1939 German synthetic production would provide 100 percent of its oil needs and half of its rubber. But in 1939 it actually accounted for only 20 percent of Germany's oil and less than 15 percent of its rubber. Two-thirds of Germany's total raw materials still came from foreign countries. The Germans also had to import 20 percent of their food.
Germany did have some advantages, however. It had the potential to expand its industrial capabilities greatly if necessary. With the absorption of Austria and the Sudetenland, Germany's population had reached 80 million, providing a good manpower pool for both industry and the armed forces. And the Russo-German economic agreement of August 1939 promised a steady flow of food, oil, and other raw materials. Hitler also expected to extract ample booty from the countries that fell under German control as a result of his Blitzkrieg.
Britain, with a population of 46 million, could not match Germany either in manpower or in its industrial base, but Britain did possess access to the resources of the rest of the world. The Commonwealth itself was a storehouse of raw materials. The British colony of Malaya alone produced 58 percent of the world's rubber. Britain, of course, could cut off Germany from overseas sources of supply by virtue of superior naval strength. Whether this would be sufficient to cause Germany critical problems was questionable in view of the 1939 Russo-German trade agreement. Hitler also had access to the resources of southeastern Europe, including Rumania's oil fields.
Britain's Achilles' heel was its dependence on large-scale imports of food and raw materials. To pay for them, the British had to maintain a high level of exports and services, such as shipping and insurance, as well as overseas investment. World War I had seriously disrupted all of these economic activities. Clearly, the outbreak of war in 1939 promised even more disastrous injury to the failing economy. In view of this dilemma, the British were reluctant to embark on an ambitious rearmament program during the 1930s. Although they finally made belated preparations for war, the results were far from impressive. The creation of new cabinet posts for supply, shipping, and food in 1939 helped lay the framework for a thoroughgoing war economy but led to little initial progress. Of more immediate importance, the British had begun to produce two excellent new fighter planes, the Hurricane and the Spitfire.
France, too, still suffered from the impact of the Great Depression. Its population of 42 million was much smaller than Germany's and even less than Britain's. France's industrial base was also much smaller than that of both countries, but the French had made some progress. Premier Daladier had appointed Paul Reynaud minister of finance in November 1938, and Reynaud had eased restrictions on investment credit and stimulated rearmament. Industrial production rose by 20 percent during the next ten months. It is indeed remarkable that France was able to enter the war on an equal basis with Germany in some respects, most notably in tanks and artillery. But the key to Anglo-French hopes for winning the war was time. If they could force Germany into a long war, their chances of victory would increase greatly. It soon became apparent, however, that time was a luxury that their alliance did not enjoy.
THE FIRST BLITZKRIEG: GERMANY'S INVASION OF POLAND
Germany first tested the Blitzkrieg in the invasion of Poland in September 1939, with spectacular results. The Poles never had a chance. Their antiquated army was at a great disadvantage in both men and equipment. The Germans committed 52 divisions (roughly 1 million men) to the campaign, including six panzer and four motorized divisions. German armor, for the most part, was not of high quality. The most numerous tank was the Panzer I, but its armament consisted of only two machine guns. The next most plentiful armored vehicle was the Panzer II, which carried a weak 20-millimeter cannon. Some higher quality Panzer IIIs and Panzer IVs were available, but in small numbers. The Panzer III mounted a 37-millimeter gun, while the Panzer IV wielded a short 75-millimeter cannon. In all, the Germans used 1,500 tanks, not a particularly large force, but together with their relatively few motorized divisions, it was more than sufficient to overwhelm the Poles.
On paper, Poland, with a population of 35 million, was capable of fielding an army of over 2 million men, but the Poles delayed mobilization until August 31 to avoid providing the Germans with an excuse for aggression. When the invasion began the following day, only 600,000 men were available. Most of this force consisted of infantry and cavalry. Poland's military leaders were exceptionally proud of their cavalry, but it was hardly a match for German armor. The Poles had only 310 tanks, most of them obsolete. They reduced their striking power still more by scattering them among infantry divisions. The Polish army had little else in the way of mechanized forces. Germany enjoyed a big advantage in air power, with 850 bombers and 400 fighters. Poland could muster a total of only 400 first-line planes, just 36 of which were modern.
Since the destruction of Czechoslovakia, German troops flanked Poland on three sides. This placed the Poles in a highly vulnerable position. Logic seemed to dictate that Polish forces should take up positions to the east of the barrier created by the Narew, Vistula, and San rivers. But this would necessitate abandoning the country's most important industrial areas. Polish leaders refused to take such drastic action. Instead, they concentrated one-third of their strength in the general area of the Polish corridor and another third in reserve between the capital, Warsaw, and the industrial city of Lodz to the southwest. They stretched the rest of their forces dangerously thin to protect the remaining border areas.
Germany divided its invading forces into Army Group North, which included two armies under the command of General Fedor von Bock, and Army Group South, consisting of three armies commanded by General Gerd von Rundstedt. Bock and Rundstedt were both Prussian aristocrats and the sons of generals. Each had served capably during World War I. At 64, Rundstedt was the senior general in the German army and highly respected for his ability as a field commander. He had actually retired in 1938 but returned to active duty a few months later. Bock's most noteworthy qualities were determination and hard work rather than brilliance. An extremely arrogant man, he was utterly devoted to the army. General Halder's OKH staff drafted the operational plan for the invasion, which was given the code name Case White. It called for the destruction of the bulk of the Polish army to the west of Warsaw by means of a pincers movement in which elements of Army Group North would swing southeastward to link up with Army Group South, which was to strike northward. Additional troops from Army Group North were to smash across the base of the Polish corridor into East Prussia, cutting off the enemy forces to the north.
The Blitzkrieg began on September 1. German armored forces quickly broke through Poland's border defenses and penetrated deep into the interior. Meanwhile, the Luftwaffe attacked the Polish air force, but contrary to a persistent myth, it did not destroy most of it on the ground. In fact, Polish planes resisted fiercely during the first few days and many Polish pilots demonstrated great heroism. German numerical and technical superiority gradually took its toll, however, and cleared the skies of enemy aircraft. Meanwhile German medium bombers and Stuka dive bombers attacked Polish troops and communications. Although actually a mediocre plane with poor speed, flimsy armor, and limited range, the Stuka worked well in this type of unopposed operation. With its fixed landing gear, the Stuka resembled a bird of prey. It was outfitted with a siren that unleashed a shrill, blood-curdling shriek as it swooped down on its victims. These features added to its impact as a weapon of terror.
Germany's most remarkable progress came in the south, where an armored corps, commanded by General Erich Hopner, sliced northeastward, reaching the outskirts of Warsaw on September 8. Another panzer corps, commanded by General Guderian, severed the Polish corridor and moved into East Prussia on September 3. The Poles fought gallantly but faced overwhelming odds. At times, when surrounded, Polish cavalry, armed with lances, actually charged German tanks rather than surrender. Confronted by these disasters, the Polish high command belatedly ordered a withdrawal of all remaining units to the Narew-Vistula-San river line.
German and Polish accounts of the cavalry charges vary. Whether myth or a valiant last stand, one thing was for sure: the Germans received only one major scare. It came on September 9, when the Poles directed a determined counterattack against the flank of Rundstedt's forces to the west of Warsaw. But after heavy fighting, the Germans blunted the Polish thrust and drove on to meet Bock's forces pushing southward. This union encircled 170,000 Polish troops, completing the pincers movement outlined in Case White.
The final phase of the Polish campaign began on September 9. It took the form of another pincers movement, which closed near Brest-Litovsk on September 17 when Guderian's panzers, swinging southward from East Prussia, met armored forces, commanded by General Ewald von Kleist, that had dashed northward from southern Poland. On the same day, Soviet troops invaded Poland from the east and quickly overran the remainder of the country. The late timing of this operation was due to the fact that the Soviets had not expected the German invasion to come so soon and were not prepared to strike earlier. A total of 90,000 Polish troops escaped into Hungary and Rumania, many of them eventually making their way to France and Britain, from where they carried on the fight.
Polish resistance continued for some time at various isolated points, including Warsaw. After reaching the suburbs of the capital on September 8, the Germans soon discovered that the narrow confines of street fighting were not well suited for attacks by armor. They resorted instead to artillery and aerial bombardment and finally launched an infantry assault on September 26. When the exhausted Polish garrison surrendered the following day, many of the people of Warsaw lay dead in the blazing ruins that comprised much of the city. The Polish capital had become the first of many European cities to experience such a fate. A few other isolated garrisons fought on in gallant but hopeless battles until as late as October 6.
The Germans had destroyed Poland with astonishing speed and thoroughness, even if the Blitzkrieg had not always functioned as flawlessly as Goebbel's propaganda machine insisted. In particular, the Luftwaffe had not completely perfected its support of the swiftly moving ground forces. Nevertheless, the Blitzkrieg had revolutionized warfare. Surprisingly, the Allies were slow to recognize this. They blamed Poland's inadequate military forces and faulty defensive plan for the disaster and assumed that it would be different when the Germans attacked in the west. The French began to have second thoughts about the potential of tanks, however, and hastily embarked on the creation of four armored divisions.
In keeping with their defensive strategy, France and Britain made no effort to stage an offensive against Germany while the Blitzkrieg was destroying Poland. The French launched only a minor probing action, despite the fact that Germany had only 25 weak reserve divisions in the west and a defensive system, the West Wall, which was far from complete and of negligible strength. But it was sufficient to impress the Western Powers, who persisted in calling it the Siegfried line after the legendary warrior of German mythology.
Ribbentrop and Soviet minister Molotov met on September 28 to petition Poland. The Soviet Union gained slightly more than half of the country and about a third of the population as well as the oil fields. Germany, although receiving a smaller amount of territory, acquired roughly two-thirds of the people, the major industrial centers, the mining regions, and the best farmland. Hitler annexed approximately half of his share, as well as Danzig, directly to Germany. He designed the remainder the "Government General" and kept it under total German domination. This arrangement gave the Germans slightly more territory than the secret protocol of August 23 had provided, but in return the Soviets received a free hand in Lithuania, which the original agreement had conceded to Germany.
Hitler had intended even before the invasion to treat the Polish people with draconian harshness. The SS now served as the instrument of his policy with the essentially passive compliance of the army, although some officers proclaimed their distaste for what was euphemistically referred to as "housecleaning." This involved the wholesale execution of Polish army officers, aristocrats, clergy and intellectuals in a concerted effort to eliminate any vestige of a ruling class. The SS also shot many Jews, a preliminary to much more thoroughgoing measures later. The Nazis intended to reduce the remaining Polish population to the role of "slaves of the Greater German World Reich." As for the Soviets, they, too, executed captured Polish army officers and resorted to mass arrests of "undesirable political elements" who were deported to Siberia and other undesirable destinations in the Soviet Union.
Stalin had mixed emotions about the destruction of Poland. To be sure, the USSR had avoided involvement in the war against Germany and had gained over half of Poland and a claim to the Baltic states. But the awesome display of German military power had disturbed the Soviet dictator. He quickly set out to create as much of a buffer zone between the Soviet Union and Germany as possible. In the next few weeks, he pressured Lithuania, Latvia, and Estonia into signing treaties that authorized the Russians to establish military, air, and naval bases on their territory.
ULTRA
Although Poland had vanished from the map, the Poles provided the Allies with the basis for one of the great technological achievements of the war. It came in the realm of military intelligence and eventually enabled the Allies to intercept and decipher German military messages and produced a wealth of information on enemy strength and intentions.
During the 1920s the Germans had developed a highly sophisticated enciphering machine, called Enigma. It was so complex that the Germans became absolutely convinced that their cyphers could not be broken. In 1929, one of these machines, en route from Berlin to the German legation in Warsaw, fell into the hands of Polish counterintelligence agents. They created an exact replica of the Enigma before allowing it to proceed to its destination and then set about breaking the German cypher. They succeeded in doing so by 1932 and read much German signal traffic during the 1930s. The Germans changed their cypher in late 1938, however, and the Poles had to undertake their task again. After Poland's defeat, many Polish cryptanalysts escaped to the West and took a few Enigma machines with them.
By April 1940, the British, with the help of the Poles, broke some of the new German codes. Unfortunately, various problems arose. All of this delayed putting their efforts to practical use for another year. Eventually, however, the achievements of the code breakers proved most valuable to the Allied cause. They also became the best-kept secret of the war and earned the code name Ultra. Still confident that their cypher could not be broken, the Germans never recognized what had happened.
A PHONY WAR OF REAL DANGER
In stark contrast to the horror of the Blitzkrieg in Poland, Western Europe remained strangely quiet during the first eight months of the war. This inactivity prompted observers to conclude that the conflict was really a fraud. Americans called it the "phony war." To the French it was the drole de guerre (literally, "odd little war"), and to the Germans the Sitzkrieg (sitting war). But the war was not as phony as it appeared. Hitler, in fact, was determined to strike in the west in the fall of 1939.
The French fully expected the Germans to attack, and Britain's military leaders agreed that Germany would strike, but Chamberlain did not expect Hitler to launch a major offensive and felt that time was on the Allies' side. The prime minister believed that the war would hurt the German economy and lead to a collapse of civilian morale. He failed to recognize that Hitler was also fighting a war of limited liability that would not require full mobilization of the economy. Germany also negotiated a second and more far-reaching economic understanding with the Soviet Union soon after the conquest of Poland. The Soviets agreed to provide Germany with grain, oil, and other raw materials in return for manufactured goods, including armaments. The Russians also supplied the Germans with rubber, tin, and other commodities that they imported from Southeast Asia.
In line with Chamberlain's vision of the fragile nature of Germany's economy as well as traditional British policy, the Allies instituted a naval blockade. But the blockade proved less effective than in World War I because of Germany's economic relationship with the USSR. The Germans countered the blockade with submarine attacks on Allied shipping, but their U-boat fleet was too small at this time to be much more than a nuisance. The British also used the period of the "phony war" to strengthen the Royal Air Force, especially their fighter planes.
Brauchitsch, Halder, and other generals were deeply concerned by Hitler's decision to attack in the west during the fall of 1939. Under no circumstances could an offensive begin before November, and this would mean a winter campaign, which they viewed as an invitation to disaster. Brauchitsch and Halder protested against the proposed offensive, but Hitler won the argument.
Hitler's intransigence led to a rebirth of the conspiracy against him that had surfaced during the Sudetenland crisis only to go into eclipse as a result of his triumph at the Munich conference. This time the conspirators went so far as to plan Hitler's assassination. The conspiracy had its nerve center in the Abwehr (Armed Forces Intelligence) and its driving force in Colonel Hans Oster, and aide to Admiral Wilhelm Canaris, the Abwehr's chief. Canaris protected Oster in his efforts while keeping his distance from the actual plot. Oster gained the support of Halder, who again consented to lead a military coup following the assassination. In fact, for a time Halder carried a pistol in his pocket, intending to shoot Hitler, but he could not quite bring himself to kill an unarmed man.
As in 1938, Brauchitsch sympathized with the conspirators but refused to become directly involved. Other leading generals, including Bock and Rundstedt, also offered sympathy but declined to implicate themselves. But Halder, too, eventually lost his nerve, fearing discovery of the plot, and took no action. Indeed, as time passed, he became more optimistic about prospects for an offensive in the west. With his defection, the conspiracy failed for a second time.
Despite Hitler's insistence on an early offensive, bad weather forced repeated postponements, and in January 1940 a German courier plane, carrying documents pertaining to the plan of attack, flew off course and made a forced landing in Belgium. Belgian authorities seized some of the documents before the Germans on board could destroy them. The Germans feared that the incident had compromised the security of their operation, and this concern, along with continuing bad weather, resulted in postponement of the offensive until May.
The capture of the documents also contributed to a decision to scrap the original invasion plan and adopt a substitute that proved infinitely superior and played a vital role in Germany's success. The old plan, code-named Case Yellow, did not promise a decisive result and held out the possibility of a renewal of the stalemate of 1914-18. It provided for primary concentration of strength, including most of the armor, in Army Group B, commanded by General von Bock. His forces were to drive through the Netherlands and Belgium into northern France before halting at the Somme River. Army Group A, under General von Rundstedt, was to drive through southern Belgium and Luxembourg in support of Bock's spearhead.
The revised plan for Case Yellow owed its inspiration in part to General Erich von Manstein, Rundstedt's chief of staff. Cold in manner and extremely outspoken, Manstein won little acclaim for his personality, but was probably the most brilliant of the German generals. Like Guderian, he had served at Verdun in 1916 and had developed a similar horror of static warfare. He offered his plan as a means of avoiding a repetition of such a dilemma. It called for the spearhead to be provided by Army Group A, which would receive additional strength, especially armor. Rundstedt's panzer forces were to drive through Luxembourg and southern Belgium and break into France near the fortress city of Sedan. Once they had accomplished this, they could pursue any of three options: swing eastward behind the Maginot line, drive toward Paris, or dash for the English Channel with the intention of cutting off Allied forces in northern France and Belgium. When the Germans finally launched their offensive in May 1940, they chose the third alternative, with amazingly successful results.
Manstein's plan also called for Bock's Army Group B to move through the Netherlands and northern Belgium as part of the overall forward movement and as a feint to lure the Allies into Belgium and away from the German spearhead. Brauchitsch and Halder originally resisted Manstein's plan as too bold. They feared an Allied counteroffensive against the German flank as Rundstedt's forces penetrated into northern France. Halder's opinion changed, however, as a result of a series of war games conducted by OKH during the winter. These confirmed that an armored thrust through the Ardennes offered the best chance at catching the Allies off balance and preventing a quick defensive response. Hitler, who was toying with a similar plan, agreed, assuring adoption of the revised version of Case Yellow, which gained formal approval on March 15.
While the Germans debated the change in Case Yellow, the Allies put the finishing touches on their own plan, with which they intended to counter the expected attack. This was Plan D, or the Dyle Plan, referring to the Dyle River in Belgium. It provided for the advance of strong French and British forces to a line based on the Dyle and Meuse rivers in central Belgium. The Allies assumed that the main German attack would come, as in 1914 and as intended in the original Case Yellow plan, through the plains of northern Belgium. They dismissed the area of Luxembourg and southern Belgium as offering no serious threat because it contained the rugged Ardennes Forest. The French believed that armored forces could not maneuver successfully in this hilly, heavily wooded terrain. As a result, Plan D stipulated that the two strongest French armies and the British Expeditionary Force would advance to the Dyle and the Meuse in Belgium while two weaker French armies took up positions opposite the Ardennes. When Hitler unleashed his attack in May, the Allies thus unwittingly sent their best troops into the jaws of the German trap and left second-rate forces in the path of Rundstedt's spearhead.
While these developments were taking place in the opposing headquarters, the "phony war" continued along the Franco-German border. There were good reasons for inactivity. The Allies were waiting for the German offensive, and the Germans, while planning to attack during the fall and winter, were unable to do so because of the weather and the change in plan. Neither side could see any point in border skirmishes that would cause casualties without being decisive.