Encyclopedia Britannica Ask the ChatbotGames & QuizzesHistory & SocietyScience & TechBiographiesAnimals & NatureGeography & TravelArts & CultureMoneyVideos World History Wars, Battles & Armed Conflicts World War II 1939-1945 Also known as: Second World War, WWII Written by , oAll Fact-checked by Last Updated: Oct 27, 2024 o Article History World War II: Germany invading Poland World War II: Germany invading Poland Germany invading Poland, September 1, 1939.Stuka 2 of 2 StukaGerman Junkers Ju 87 "Stuka" dive-bomber. 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.Also called: Second World War Date: September 3, 1939 - September 2, 1945 Participants: Canada China France Germany India Italy Japan Soviet Union United Kingdom United States Major Events: Battle of Crete atomic bombings of Hiroshima and Nagasaki Battle of Saipan Battle of Moscow Invasion of Poland Key People: Winston Churchill Adolf Hitler Alessandro Pertini Franklin D. Roosevelt Edward O'Hare On the Web: Academia - Forgotten alliance: Hitler-Stalin pact of 1939 and the outcome of Second World War (Oct.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 26.23, 2024) (Read Sir John Keegan's Britannica entry on the Normandy Invasion.) Axis initiative and Allied reaction The outbreak of war By the early part of 1939 the German dictator Adolf Hitler had become determined to invade and occupy Poland.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.In September 1939 the Allies, namely Great Britain, France, and Poland, were together superior in industrial resources, population, and military manpower, but the German military, or Wehrmacht, because of its armament, training, doctrine, discipline, and fighting spirit, was the most efficient and effective fighting force for its size in the world.Allied air strength, September 1939 aircraft British French Polish bombers 536 463 200 fighters 608 634 300 reconnaissance 96 444 -- coastal command 216 -- -- fleet air arm 204 194 -- Great Britain, which was held back by delays in the rearmament program, was producing one modern fighter in 1939, the Hurricane.News o Italy's government pays homage to fascist defeat in key WWII battle, sparking opposition criticism o Oct. 26, 2024, 2:06 AM ET (ABC News (U.S.)) World War II, conflict that involved virtually every part of the world during the years 1939-45.Britannica Quiz Pop Quiz: 17 Things to Know About World War II Forces and resources of the European combatants, 1939 Adolf Hitler Adolf HitlerAdolf Hitler reviewing German troops in Poland, September 1939.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).The war was in many respects a continuation, after an uneasy 20-year hiatus, of the disputes left unsettled by World War I. 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.The principal belligerents were the Axis powers--Germany, Italy, and Japan--and the Allies--France, Great Britain, the United States, the Soviet Union, and, to a lesser extent, China.Atomic bombing of Hiroshima 2 of 2 Atomic bombing of HiroshimaA gigantic mushroom cloud rising above Hiroshima, Japan, on August 6, 1945, after a U.S. aircraft dropped an atomic bomb on the city, immediately killing more than 70,000 people.View archival footage of German troops invading Poland and forcing Europe into war View archival footage of German troops invading Poland and forcing Europe into warIn September 1939 the Germans overrun Poland, forcing all of Europe into a state of war.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.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.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.World War II events 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 German aircraft production by year year combat types other types 1933 0 368 1934 840 1,128 1935 1,823 1,360 1936 2,530 2,582 1937 2,651 2,955 1938 3,350 1,885 1939 4,733 3,562 The standardization of engines and airframes gave the Luftwaffe an advantage over its opponents.What countries fought in World War II?