World War II, also called Second World War, conflict that involved virtually every part of the world during the years 1939–45. The principal were the , , and japan—and the Allies—France, Great Britain , the United States , the Soviet union , and, to a lesser extent, China. The war was in many respects a continuation, after an uneasy 20-year hiatus,of the disputes world war 1. The 40,000,000–50,000,000 deaths incurred in World War II make it the bloodiest conflict, as well as the largest war, in history.
Along with World War I, World War II was one of the great watersheds of 20th-century geopolitical history. It resulted in the extension of the Soviet Union’s power to nations of eastern Europe , enabled a communist movement to eventually achieve power in China, and marked the decisive shift of power in the world away from the states of western Europe and toward the United States and the Soviet Union.
The outbreak of war
By the early part of 1939 Gemern dictator Adolf Hitler had become determined to invade and occupy poland. Poland, for its part, had guarantees of French and British military support should it be attacked by Germany. Hitler intended to invade Poland anyway, but first he had to neutralize the possibility that the Soviet Union would resist the invasion of its western neighbour. Secret negotiations led on August 23–24 to the signing of the German- in MOSCOW . In a secret Protocol of this pact, the Germans and the Soviets agreed that Poland should be divided between them, with the western third of the country going to Germany and the eastern two-thirds being taken over by the U.S.S.R.
Having achieved this cynical agreement, the other provisions of which stupefied Europe even without divulgence of the secret protocol, Hitler thought that Germany could attack Poland with no danger of Soviet or British intervention and gave orders for the invasion to start on August 26. News of the signing, on August 25, of a formal treaty of mutual assistance between Great Britain and Poland (to supersede a previous though temporary agreement) caused him to postpone the start of hostilities for a few days. He was still determined, however, to ignore the diplomatic efforts of the western powers to restrain him. Finally, at 12:40 pm on August 31, 1939, Hitler ordered hostilities against Poland to start at 4:45 the next morning. The invasion began as ordered. In response, Great Brritain and Francerance declared war on Germany on September 3, at 11:00 am and at 5:00 pm, respectively. World War II had begun.
Forces and resources of the European combatants, 1939
In September 1939 the Allies, namely Great Britain, France, and poland, were together superior in industrial resources, population, and military manpower, but the German Army, or weehrmacht, because of its armament, training, doctrines, descipline, and fighting spirit, was the most efficient and effective fighting force for its size in the world. The index of military strength in September 1939 was the number of divisions that each nation could mobilize. Against Germany’s 100 infantry divisions and six armoured divisions, France had 90 infantry divisions in metropolitan France, Great Britain had 10 infantry divisions, and Poland had 30 infantry divisions, 12 cavalry brigades, and one armoured brigade (Poland had also 30 reserve infantry divisions, but these could not be mobilized quickly). A division contained from 12,000 to 25,000 men.
It was the qualitative superiority of the German infantry divisions and the number of their armoured divisions that made the difference in 1939. The firepower of a German infantry division far exceeded that of a French, British, or Polish division; the standard German division included 442 machine guns, 135 mortars, 72 antitank guns, and 24 howitzers. Allied divisions had a firepower only slightly greater than that of World War I. Germany had six armoured divisions in September 1939; the Allies, though they had a large number of tanks, had no armoured divisions at that time.
The six armoured, or panzer, divisions of the Wehrmacht comprised some 2,400 tanks. And though Germany would subsequently expand its tank forces during the first years of the war, it was not the number of tanks that Germany had (the Allies had almost as many in September 1939) but the fact of their being organized into divisions and operated as such that was to prove decisive. In accordance with the doctrines of General Heinz Guderian, the German tanks were used in massed formations in conjunction with motorized artillery to punch holes in the enemy line and to isolate segments of the enemy, which were then surrounded and captured by motorized German infantry divisions while the tanks ranged forward to repeat the process: deep drives into enemy territory by panzer divisions were thus followed by mechanized infantry and foot soldiers. These tactics were supported by dive bombers that attacked and disrupted the enemy’s supply and communications lines and spread panic and confusion in its rear, thus further paralyzing its defensive capabilities. Mechanization was the key to the German blitzkrieg, or “lightning war,” so named because of the unprecedented speed and mobility that were its salient characteristics. Tested and well-trained in maneuvers, the German panzer divisions constituted a force with no equal in Europe.
The German Air Force, or Luftwaffe, was also the best force of its kind in 1939. It was a ground-cooperation force designed to support the Army, but its planes were superior to nearly all Allied types. In the rearmament period from 1935 to 1939 the production of German combat aircraft steadily mounted. The table shows the production of German aircraft by years.
The standardization of engines and airframes gave the Luftwaffe an advantage over its opponents. Germany had an operational force of 1,000 fighters and 1,050 bombers in September 1939. The Allies actually had more planes in 1939 than Germany did, but their strength was made up of many different types, some of them obsolescent. The corresponding table shows the number of first-line military aircraft available to the Allies at the outbreak of war.
Great Britain, which was held back by delays in the rearmament program, was producing one modern fighter in 1939, the Hurricane. A higher-performance fighter, the Spitfire, was just coming into production and did not enter the air war in numbers until 1940.
The value of the French Air Force in 1939 was reduced by the number of obsolescent planes in its order of battle: 131 of the 634 fighters and nearly all of the 463 bombers. France was desperately trying to buy high-performance aircraft in the United States in 1939.
At sea the odds against Germany were much greater in September 1939 than in August 1914, since the Allies in 1939 had many more large surface warships than Germany had. At sea, however, there was to be no clash between the Allied and the German massed fleets but only the individual operation of German pocket battleships and commerce raiders.
Technology of war, 1918–39
When World War I ended, the experience of it seemed to vindicate the power of the defensive over the offensive. It was widely believed that a superiority in numbers of at least three to one was required for a successful offensive. Defensive concepts underlay the construction of the Maginot Line between France and Germany and of its lesser counterpart, the Siegfried Line, in the interwar years. Yet by 1918 both of the requirements for the supremacy of the offensive were at hand: tanks and planes. The battles of Cambrai (1917) and Amiens (1918) had proved that when tanks were used in masses, with surprise, and on firm and open terrain, it was possible to break through any trench system.
The Germans learned this crucial, though subtle, lesson from World War I. The Allies on the other hand felt that their victory confirmed their methods, weapons, and leadership, and in the interwar period the French and British armies were slow to introduce new weapons, methods, and doctrines. Consequently, in 1939 the British Army did not have a single armoured division, and the French tanks were distributed in small packets throughout the infantry divisions. The Germans, by contrast, began to develop large tank formations on an effective basis after their rearmament program began in 1935. In the air the technology of war had also changed radically between 1918 and 1939. Military aircraft had increased in size, speed, and range, and for operations at sea, aircraft carriers were developed that were capable of accompanying the fastest surface ships. Among the new types of planes developed was the dive bomber, a plane designed for accurate low-altitude bombing of enemy strong points as part of the tank-plane-infantry combination. Fast low-wing monoplane fighters were developed in all countries; these aircraft were essentially flying platforms for eight to 12 machine guns installed in the wings. Light and medium bombers were also developed that could be used for the strategic bombardment of cities and military strongpoints. The threat of bomber attacks on both military and civilian targets led directly to the development of radar in England. Radar made it possible to determine the location, the distance, and the height and speed of a distant aircraft no matter what the weather was. By December 1938 there were five radar stations established on the coast of England, and 15 additional stations were begun. So, when war came in September 1939, Great Britain had a warning chain of radar stations that could tell when hostile planes were approaching. The campaign in Poland, 1939 The German conquest of Poland in September 1939 was the first demonstration in war of the new theory of high-speed armoured warfare that had been adopted by the Germans when their rearmament began. Poland was a country all too well suited for such a demonstration. Its frontiers were immensely long—about 3,500 miles in all; and the stretch of 1,250 miles adjoining German territory had recently been extended to 1,750 miles in all by the German occupation of Bohemia-Moravia and of Slovakia, so that Poland’s southern flank became exposed to invasion—as the northern flank, facing East Prussia, already was. Western Poland had become a huge salient that lay between Germany’s jaws.
It would have been wiser for the Polish Army to assemble farther back, behind the natural defense line formed by the Vistula and San rivers, but that would have entailed the abandonment of some of the most valuable western parts of the country, including the Silesian coalfields and most of the main industrial zone, which lay west of the river barrier. The economic argument for delaying the German approach to the main industrial zone was heavily reinforced by Polish national pride and military overconfidence.
When war broke out the Polish Army was able to mobilize about 1,000,000 men, a fairly large number. The Polish Army was woefully outmoded, however, and was almost completely lacking in tanks, armoured personnel carriers, and antitank and antiaircraft guns. Yet many of the Polish military leaders clung to the double belief that their preponderance of horsed cavalry was an important asset and that they could take the offensive against the German mechanized forces. They also tended to discount the effect of Germany’s vastly superior air force, which was nearly 10 times as powerful as their own.
The unrealism of such an attitude was repeated in the Polish Army’s dispositions. Approximately one-third of Poland’s forces were concentrated in or near the Polish Corridor (in northeastern Poland), where they were perilously exposed to a double envelopment—from East Prussia and the west combined. In the south, facing the main avenues of a German advance, the Polish forces were thinly spread. At the same time, nearly another one-third of Poland’s forces were massed in reserve in the north-central part of the country, between Łódź and Warsaw, under the commander in chief, Marshal Edward Rydz-Śmigły. The Poles’ forward concentration in general forfeited their chance of fighting a series of delaying actions, since their foot-marching army was unable to retreat to their defensive positions in the rear or to man them before being overrun by the invader’s mechanized columns.
The 40-odd infantry divisions employed by the Germans in the invasion counted for much less than their 14 mechanized or partially mechanized divisions: these consisted of six armoured divisions; four light divisions, consisting of motorized infantry (infantry wholly transported by trucks and personnel carriers) with two armoured units; and four motorized divisions. The Germans attacked with about 1,500,000 troops in all. It was the deep and rapid thrusts of these mechanized forces that decided the issue, in conjunction with the overhead pressure of the Luftwaffe, which wrecked the Polish railway system and destroyed most of the Polish Air Force before it could come into action. The Luftwaffe’s terror-bombing of Polish cities, bridges, roads, rail lines, and power stations completed the disorganization of the Polish defenses.
On September 1, 1939, the German attack began. Against northern Poland, General Fedor von Bock commanded an army group comprising General Georg von Küchler’s 3rd Army, which struck southward from East Prussia, and General Günther von Kluge’s 4th Army, which struck eastward across the base of the Corridor. Much stronger in troops and in tanks, however, was the army group in the south under General Gerd von Rundstedt, attacking from Silesia and from the Moravian and Slovakian border: General Johannes Blaskowitz’s 8th Army, on the left, was to drive eastward against Łódź; General Wilhelm List’s 14th Army, on the right, was to push on toward Kraków and to turn the Poles’ Carpathian flank; and General Walther von Reichenau’s 10th Army, in the centre, with the bulk of the group’s armour, was to deliver the decisive blow with a northwestward thrust into the heart of Poland. By September 3, when Kluge in the north had reached the Vistula and Küchler was approaching the Narew River, Reichenau’s armour was already beyond the Warta; two days later his left wing was well to the rear of Łódź and his right wing at Kielce; and by September 8 one of his armoured corps was in the outskirts of Warsaw, having advanced 140 miles in the first week of war. Light divisions on Reichenau’s right were on the Vistula between Warsaw and Sandomierz by September 9, while List, in the south, was on the San above and below Przemyśl. At the same time, the 3rd Army tanks, led by Guderian, were across the Narew attacking the line of the Bug River, behind Warsaw. All the German armies had made progress in fulfilling their parts in the great enveloping maneuver planned by General Franz Halder, chief of the general staff, and directed by General Walther von Brauchitsch, the commander in chief. The Polish armies were splitting up into uncoordinated fragments, some of which were retreating while others were delivering disjointed attacks on the nearest German columns.
On September 10 the Polish commander in chief, Marshal Edward Rydz-Śmigły, ordered a general retreat to the southeast. The Germans, however, were by that time not only tightening their net around the Polish forces west of the Vistula (in the Łódź area and, still farther west, around Poznań) but also penetrating deeply into eastern Poland. The Polish defense was already reduced to random efforts by isolated bodies of troops when another blow fell: on September 17, 1939, Soviet forces entered Poland from the east. The next day, the Polish government and high command crossed the Romanian frontier on their way into exile. The Warsaw garrison held out against the Germans until September 28, undergoing terror-bombings and artillery barrages that reduced parts of the city to rubble, with no regard for the civilian population. The last considerable fragment of the Polish Army resisted until October 5; and some guerrilla fighting went on into the winter. The Germans took a total of 700,000 prisoners, and about 80,000 Polish soldiers escaped over neutral frontiers. Approximately 70,000 Polish soldiers were killed and more than 130,000 wounded during the battle, whereas the Germans sustained about 45,000 total casualties. Poland was conquered for partition between Germany and the U.S.S.R., the forces of which met and greeted each other on Polish soil. On September 28 another secret German–Soviet protocol modified the arrangements of August: all Lithuania was to be a Soviet sphere of influence, not a German one; but the dividing line in Poland was changed in Germany’s favour, being moved eastward to the Bug River. The Baltic states and the Russo-Finnish War, 1939–40
The invaders succeeded in isolating the little Arctic port of Petsamo in the far north but were ignominiously repulsed on all of the fronts chosen for their advance. On the Karelian Isthmus, the massive reinforced-concrete fortifications of Finland’s Mannerheim Line blocked the Soviet forces’ direct land route from Leningrad into Finland. The Soviet planners had grossly underestimated the Finns’ national will to resist and the natural obstacles constituted by the terrain’s numerous lakes and forests. The western powers exulted overtly over the humiliation of the Soviet Union. One important effect of Finland’s early successes was to reinforce the tendency of both Hitler and the western democracies to underestimate the Soviet military capabilities. But in the meantime, the Soviet strategists digested their hard-learned military lessons. On February 1, 1940, the Red Army launched 14 divisions into a major assault on the Mannerheim Line. The offensive’s weight was concentrated along a 10-mile sector of the line near Summa, which was pounded by a tremendous artillery bombardment. As the fortifications were pulverized, tanks and sledge-carried infantry advanced to occupy the ground while the Soviet Air Force broke up attempted Finnish counterattacks. After little more than a fortnight of this methodical process, a breach was made through the whole depth of the Mannerheim Line. Once the Soviets had forced a passage on the Karelian Isthmus, Finland’s eventual collapse was certain. On March 6 Finland sued for peace, and a week later the Soviet terms were accepted: the Finns had to cede the entire Karelian Isthmus, Viipuri, and their part of the Rybachy Peninsula to the Soviets. The Finns had suffered about 70,000 casualties in the campaign, the Soviets more than 200,000. The war in the west, September 1939–June 1940 During their campaign in Poland, the Germans kept only 23 divisions in the west to guard their frontier against the French, who had nearly five times as many divisions mobilized. The French commander in chief, General Maurice-Gustave Gamelin, proposed an advance against Germany through neutral Belgium and the Netherlands in order to have room to exercise his ponderous military machine. He was overruled, however, and French assaults on the 100-mile stretch of available front along the Franco-German frontier had barely dented the German defenses when the collapse of Poland prompted the recall of Gamelin’s advanced divisions to defensive positions in the Maginot Line. From October 1939 to March 1940, successive plans were developed for counteraction in the event of a German offensive through Belgium—all of them based on the assumption that the Germans would come across the plain north of Namur, not across the hilly and wooded Ardennes. The Germans would indeed have taken the route foreseen by the French if Hitler’s desire for an offensive in November 1939 had not been frustrated, on the one hand, by bad weather and, on the other, by the hesitations of his generals; but in March 1940 the bold suggestion of General Erich von Manstein that an offensive through the Ardennes should, in fact, be practicable for tank forces was adopted by Hitler, despite orthodox military opinion. Meanwhile, Hitler’s immediate outlook had been changed by considerations about Scandinavia. Originally he had intended to respect Norway’s neutrality. Then rumours leaked out, prematurely, of British designs on Norway—as, in fact, Winston Churchill, first lord of the Admiralty, was arguing that mines should be laid in Norwegian waters to stop the export of Swedish iron ore from Gällivare to Germany through Norway’s rail terminus and port of Narvik. The British Cabinet, in response to Churchill, authorized at least the preparation of a plan for a landing at Narvik; and in mid-December 1939 a Norwegian politician, Vidkun Quisling, leader of a pro-Nazi party, was introduced to Hitler. On January 27, 1940, Hitler ordered plans for an invasion of Norway, for use if he could no longer respect Norway’s neutrality. After France’s failure to interrupt the German conquest of Poland, the western powers and the Germans were so inactive with regard to land operations that journalists began to speak derisively, over the next six months, of the “phony war.” At sea, however, the period was somewhat more eventful. German U-boats sank the British aircraft carrier Courageous (September 17) and the battleship Royal Oak (October 14). The U-boats’ main warfare, however, was against merchant shipping: they sank more than 110 vessels in the first four months of the war. Both the Germans and the British, meanwhile, were engaged in extensive mine laying. In surface warfare at sea, the British were on the whole more fortunate than the Germans. A German pocket battleship in the Atlantic, the Admiral Graf Spee sank nine ships before coming to a tragic end: having sustained and inflicted damage in an engagement with three British cruisers off the Río de la Plata on Dec. 13, 1939, she made off to Montevideo and obtained leave to spend four days there for repairs; the British mustered reinforcements for the two cruisers still capable of action after the engagement, namely the Ajax and the Achilles, and brought the Cumberland to the scene in time; but, on December 17, when the Graf Spee put to sea again, her crew scuttled her a little way out of the harbour before the fight could be resumed.
The invasion of Norway British plans for landings on the Norwegian coast in the third week of March 1940 were temporarily postponed. Prime Minister Neville Chamberlain, however, was by that time convinced that some aggressive action ought to be taken; and Paul Reynaud, who succeeded Édouard Daladier as France’s premier on March 21, was of the same opinion. (Reynaud had come into office on the surge of the French public’s demand for a more aggressive military policy and quicker offensive action against Germany.) It was agreed that mines should be laid in Norwegian waters and that the mining should be followed by the landing of troops at four Norwegian ports, Narvik, Trondheim, Bergen, and Stavanger. Because of Anglo-French arguments, the date of the mining was postponed from April 5 to April 8. The postponement was catastrophic. Hitler had on April 1 ordered the German invasion of Norway to begin on April 9; so, when on April 8 the Norwegian government was preoccupied with earnest protest about the British mine laying, the German expeditions were well on their way. On April 9, 1940, the major Norwegian ports from Oslo northward to Narvik (1,200 miles away from Germany’s naval bases) were occupied by advance detachments of German troops. At the same time, a single parachute battalion (the first ever employed in warfare) took the Oslo and Stavanger airfields, and 800 operational aircraft overawed the Norwegian population. Norwegian resistance at Narvik, at Trondheim (the strategic key to Norway), at Bergen, at Stavanger, and at Kristiansand had been overcome very quickly; and Oslo’s effective resistance to the seaborne forces was nullified when German troops from the airfield entered the city. Simultaneously, along with their Norwegian enterprise, the Germans on April 9 occupied Denmark, sending troopships, covered by aircraft, into Copenhagen harbour and marching over the land frontier into Jutland. This occupation was obviously necessary for the safety of their communications with Norway. Allied troops began to land at Narvik on April 14. Shortly afterward, British troops were landed also at Namsos and at Åndalsnes, to attack Trondheim from the north and from the south, respectively. The Germans, however, landed fresh troops in the rear of the British at Namsos and advanced up the Gudbrandsdal from Oslo against the force at Åndalsnes. By this time the Germans had about 25,000 troops in Norway. By May 2, both Namsos and Åndalsnes were evacuated by the British. The Germans at Narvik held out against five times as many British and French troops until May 27. By that time the German offensive in France had progressed to such an extent that the British could no longer afford any commitment in Norway, and the 25,000 Allied troops were evacuated from Narvik 10 days after their victory. The Norwegian king Haakon VII and his government left Norway for Britain at the same time. Hitler garrisoned Norway with about 300,000 troops for the rest of the war. By occupying Norway, Hitler had ensured the protection of Germany’s supply of iron ore from Sweden and had obtained naval and air bases with which to strike at Britain if necessary.
Profiting quickly from its understanding with Germany, the U.S.S.R. on October 10, 1939, constrained Estonia, Latvia, and Lithuania to admit Soviet garrisons onto their territories. Approached with similar demands, Finland refused to comply, even though the U.S.S.R. offered territorial compensation elsewhere for the cessions that it was requiring for its own strategic reasons. Finland’s armed forces amounted to about 200,000 troops in 10 divisions. The Soviets eventually brought about 70 divisions (about 1,000,000 men) to bear in their attack on Finland, along with about 1,000 tanks. Soviet troops attacked Finland on November 30, 1939.