If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Beginning of World War II

World War II, the largest and bloodiest conflict in human history, started with Japan's increasing militarism and nationalism in the early 1900s. Japan occupied Korea and invaded Manchuria, exploiting China's civil war. Meanwhile, Hitler's Germany and Mussolini's Italy grew more militaristic, leading to Germany's invasion of Poland, marking the formal start of World War II.

Want to join the conversation?

  • starky seedling style avatar for user Anne Frank
    What was Canada's role in all this?
    (63 votes)
    Default Khan Academy avatar avatar for user
    • aqualine ultimate style avatar for user Shay Kirkland
      Canada entered into WWII on September 10th 1939. The first contingents of Canadian troops arrived in the United Kingdom with in two months, to supplement the BEF (British Expeditionary Forces.) Canada's role in the British Isles was one of defense. Canadian forces also arrived in Hong Kong in time to meet the Japanese invasion fighting alongside the British, Indian, and Hong Kong forces in defense of the colony until the Christmas Day (1941) surrender.

      Canada assisted by land sea and air. By Land Canadian units played a major role in the liberation of the Netherlands, and the Battle of Germany. By sea the RCN (Royal Canadian Navy) grew near 100,00 personnel, and close to 400 vessels. They mainly acted as convoy escorts in the Atlantic, Mediterranean, and to Murmansk in the USSR. In addition the supported amphibious landings. 48 squadrons of the RCAF (Royal Canadian Air Force) served in Europe. Canadian airmen fought in the Battle of Britain, North Africa, Italy, and the Normandy invasion.
      (99 votes)
  • aqualine ultimate style avatar for user inirah
    Why did Britain and France declare war on Germany? Is Poland in an agreement with them or something? Why did they have to declare war when Germany invaded Poland, it’s not like Germany was invading France and Britain right?
    (13 votes)
    Default Khan Academy avatar avatar for user
    • primosaur sapling style avatar for user Goldleaf
      Britain and France declared war on Germany because they had warned Hitler that he was going too far invading countries (such as Czechoslovakia and Austria) and if he invaded Poland, it would mean war. Poland was being protected by Britain and France, as it had been reinstated as a country only a couple decades ago at the treaty of Versallies.
      (23 votes)
  • leafers ultimate style avatar for user jacobthomaskurian
    at he says china is in a civil war with japan. but in civil wars it is one country fights themselves.
    (6 votes)
    Default Khan Academy avatar avatar for user
  • hopper cool style avatar for user ║GoUSA║
    What made the Second Sino-Japanese War so bloody?
    (7 votes)
    Default Khan Academy avatar avatar for user
    • leaf green style avatar for user Alexander Wu
      The Japanese had superior weapons (the US sold stuff to them at first). They had planes, ships, artillery, tanks, etc, while the Chinese barely had enough ammunition. The Chinese were doing anything they could to stop them from entering the city (battle of Shanghai), instead of putting priority on preserving lives of soldiers. This is because they had to get the people, supplies, and factories into the mainland to maintain long term warfare (which was their only hope of victory). So they were basically sending people into a suicide box.
      (14 votes)
  • winston default style avatar for user Gabriel's happy like Winston!
    why are they called the national National Socialist German Workers' Party if they hate socialism?
    (6 votes)
    Default Khan Academy avatar avatar for user
    • hopper cool style avatar for user Wanli Tan
      They're kinda complicated. See, the NSGWP emerged from German Nationalists that fought against Communistic uprisings in WWI. They attracted workers away from Communistic parties, but they themselves opposed the burgeoise. Kinda ironic, not sure why, but they would immediately revert themselves to their Anti-Marxism form in the 30s.
      (7 votes)
  • hopper cool style avatar for user Matthew
    Why did japan want to take over so many places?
    (5 votes)
    Default Khan Academy avatar avatar for user
    • aqualine ultimate style avatar for user su
      Similar to how Hitler intended on Germany's global expansion and annexed so many countries in the western hemisphere, Japan was another country that wanted to do the same thing. Japan, however, focused on expanding in Asia and exercise control there. The Pacific Theater refers to the part of world war 2 in which Japan had a big role to play.

      Hope I could answer your question
      (7 votes)
  • blobby green style avatar for user olivia.smith
    I know the US is coming out of a depression in the late 30s... had the rest of the globe already recovered? If not, how did a depression impact the start/course of WWII?
    (5 votes)
    Default Khan Academy avatar avatar for user
    • starky tree style avatar for user Aydia C
      Reparations imposed on Germany following WWI left the company poorer and economic woes caused resentment amongst its population. The Great Depression of the 1930s and a collapse in international trade also worsened the economic situation in Europe, allowing Hitler to rise to power on the promise of revitalization.
      (5 votes)
  • winston default style avatar for user :|
    What was Hitler's motive for ww2?
    (3 votes)
    Default Khan Academy avatar avatar for user
    • piceratops ultimate style avatar for user Hecretary Bird
      Hitler wanted to restore Germany to greatness, which involved both it being the dominant empire over the rest of the world and the "Aryan race" rising to power. Hitler saw how Germany was forced to bow to the Allies following World War 1, and saw the state Germany was reduced to because of the enormous reparations it was made to pay in the treaty of Versailles. He wished to make Germany great again, and one way that this would happen is if the Aryan race were the masters of others (people thought the Aryans were a better race than others and that they originated in Germany and Scandinavia). He believed that the Jews were the cause of Germany's poverty. To accomplish Hitler's goal, Germany needed to take over other countries or have them assimilate into them. Opposing ideals and inferior people needed to be crushed.
      (10 votes)
  • starky ultimate style avatar for user ®oman
    How do you classify something as a World War?
    (4 votes)
    Default Khan Academy avatar avatar for user
    • boggle blue style avatar for user Davin V Jones
      There is no official definition/classification. It is just a descriptive name applied to those particular conflicts. Some scholars have suggested that World War could easily be applied to other earlier conflicts as well, such as the seven years war, or the Napoleonic wars.
      (4 votes)
  • aqualine ultimate style avatar for user Caleb Mitchell
    Why did japan all of a sudden want to challenge a international superpower like China? Resources? More land to create more farms for its agriculture?
    (1 vote)
    Default Khan Academy avatar avatar for user
    • leaf blue style avatar for user Yohan Lee
      Geologically Japan is an island, the island formed because of the tectonic plates beneath them so there are always earthquakes, volcanic eruptions, large tsunamis. Japan isn't suitable for sustaining big farms and domestic animals for a long period of time.
      There were always Japanese invasions toward Korea like the Imjin War and the Chungyu War(1592–1598)and other small big wars before and after that. The growing population and the idea of imperialism also the adoption of modern technology from the western countries gave them a chance to take over Korea in the forced treaty of Japan-Korea Annexation 1910. Taking over Korea gave them power, more resources, confidence, and land. They could put their troops in Korea and attack more easily upward to Manchuria and China.
      In order to support the growing economy and military, the resource full Chinese territory was in Japan's eyes. The Chinese government was kind of weak in a way at that time while uniting its people, Japan attacked China with no declaration of war brutally killing residents and also forcing Koreans to join the war, making the Japanese territory spread like wildfire. There were lots of war crimes also made by Japan.
      Wish they will be more sorry about the war crimes to the neighboring countries and wish there will be no more wars in this world...
      (7 votes)

Video transcript

World War II was the largest conflict in all of human history. The largest and bloodiest conflict And so you can imagine it is quite complex My goal in this video is to start giving us a survey, an overview of the war. And I won't even be able to cover it all in this video. It is really just a think about how did things get started. Or what happened in the lead up? And to start I am actually going to focus on Asia and the Pacific. Which probably doesn't get enough attention when we look at it from a western point of view But if we go back even to the early 1900s. Japan is becoming more and more militaristic. More and more nationalistic. In the early 1900s it had already occupied... It had already occupied Korea as of 1910. and in 1931 it invades Manchuria. It invades Manchuria. So this right over here, this is in 1931. And it installs a puppet state, the puppet state of Manchukuo. And when we call something a puppet state, it means that there is a government there. And they kind of pretend to be in charge. But they're really controlled like a puppet by someone else. And in this case it is the Empire of Japan. And we do remember what is happening in China in the 1930s. China is embroiled in a civil war. So there is a civil war going on in China. And that civil war is between the Nationalists, the Kuomintang and the Communists versus the Communists The Communists led by Mao Zedong. The Kuomintang led by general Chiang Kai-shek. And so they're in the midst of the civil war. So you can imagine Imperial Japan is taking advantage of this to take more and more control over parts of China And that continues through the 30s until we get to 1937. And in 1937 the Japanese use some pretext with, you know, kind of a false flag, kind of... well, I won't go into the depths of what started it kind of this Marco-Polo Bridge Incident But it uses that as justifications to kind of have an all-out war with China so 1937...you have all-out war and this is often referred to as the Second Sino-Japanese War ...Sino-Japanese War Many historians actually would even consider this the beginning of World War II. While, some of them say, ok this is the beginning of the Asian Theater of World War II of the all-out war between Japan and China, but it isn't until Germany invades Poland in 1939 that you truly have the formal beginning, so to speak, of World War II. Regardless of whether you consider this the formal beginning or not, the Second Sino-Japanese War, and it's called the second because there was another Sino-Japanese War in the late 1800s that was called the First Sino-Japanese War, this is incredibly, incredibly brutal and incredibly bloody a lot of civilians affected we could do a whole series of videos just on that But at this point it does become all-out war and this causes the civil war to take a back seat to fighting off the aggressor of Japan in 1937. So that lays a foundation for what's happening in The Pacific, in the run-up to World War II. And now let's also remind ourselves what's happening... what's happening in Europe. As we go through the 1930s Hitler's Germany, the Nazi Party, is getting more and more militaristic. So this is Nazi Germany... Nazi Germany right over here. They're allied with Benito Mussolini's Italy. They're both extremely nationalistic; they both do not like the Communists, at all You might remember, that in 1938... 1938, you have the Anschluss, which I'm sure I'm mispronouncing, and you also have the takeover of the Sudetenland in Czechoslovakia. So the Anschluss was the unification with Austria and then you have the Germans taking over the of Sudetenland in Czechoslovakia and this is kind of the famous, you know, the rest of the, what will be called the Allied Powers kind of say, "Okay, yeah, okay maybe Hitler's just going to just do that... well we don't want to start another war. We still all remember World War I; it was really horrible. And so they kind of appease Hitler and he's able to, kind of, satisfy his aggression. so in 1938 you have Austria, Austria and the Sudetenland ...and the Sudetenland... are taken over, are taken over by Germany and then as you go into 1939, as you go into 1939 in March they're able to take over all of Czechoslovakia they're able to take over all of Czechoslovakia and once again the Allies are kind of, they're feeling very uncomfortable, they kind of, have seen something like this before they would like to push back, but they still are, kind of, are not feeling good about starting another World War so they're hoping that maybe Germany stops there. So let me write this down... So all of Czechoslovakia... ...Czechoslovakia... is taken over by the Germans. This is in March of 1939. And then in August you have the Germans, and this is really in preparation for, what you could guess is about to happen, for the all-out war that's about to happen the Germans don't want to fight the Soviets right out the gate, as we will see, and as you might know, they do eventually take on the Soviet Union, but in 1939 they get into a pact with the Soviet Union. And so this is, they sign the Molotov–Ribbentrop Pact with the Soviet Union, this is in August, which is essentially mutual non-aggression "Hey, you know, you do what you need to do, we know what we need to do." and they secretly started saying "Okay were gonna, all the countries out here, we're going to create these spheres of influence where Germany can take, uh, control of part of it and the Soviet Union, and Stalin is in charge of the Soviet Union at this point, can take over other parts of it. And then that leads us to the formal start where in September, let me write this in a different color... so September of 1939, on September 1st, Germany invades Poland Germany invades Poland on September 1st, which is generally considered the beginning of World War II. and then you have the Great Britain and France declares war on Germany so let me write this World War II... starts everyone is declaring war on each other, Germany invades Poland, Great Britain and France declare war on Germany, and you have to remember at this point Stalin isn't so concerned about Hitler he's just signed the Molotov-Ribbentrop Pact and so in mid-September, Stalin himself invades Poland as well so they both can kind of carve out... ...their spheres of influence... so you can definitely sense that things are not looking good for the world at this point you already have Asia in the Second Sino-Japanese War, incredibly bloody war, and now you have kind of, a lot of very similar actors that you had in World War I and then they're starting to get into a fairly extensive engagement.