World War II Overview

World War II Overview Video

Hi, and welcome to this video on World War II. Today, we’ll be looking at an overview of the origins, key events, and themes of the Second World War.

This won’t just be a summary of the war in Europe; we’ll also look at the Pacific theater and the importance of the home front, how entire societies were mobilized to sustain such a monumental war effort, and we’ll also briefly look at the key outcomes and how they shaped the world as we know it today.

To begin, let’s quickly remind ourselves of the highlights of World War I.

World War I Overview

Put simply, the world’s major powers fought a grueling war of attrition from 1914-1918. It was a global conflict but the most important theater of the war was the Western Front: two opposing lines of trenches stretching across Western Europe. After suffering heavy losses, the Allies finally triumphed over the Central Powers. The fighting came to an end on November 11, 1918, when the German Empire signed an armistice with Britain, France, and the United States. After several months of negotiation, the Treaty of Versailles was signed on June 28, 1919.

For the defeated Germans, the treaty seemed harsh and the cause of years of bitter resentment. They were forced to accept responsibility for causing the war and required to pay huge reparations. For the French, the treaty was quite lenient and a German revival was the cause of a great deal of anxiety. Ferdinand Foch, a French general, famously declared that Versailles was not a peace but a twenty-year armistice. He was right.

Hitler and the Nazi Party

The years following World War I were a bleak period of European history, particularly in Germany. The humiliation of Versailles and a global economic downturn caused hyperinflation, massive unemployment, and political violence. These were the conditions which allowed extremist voices to be heard, and–in January 1933–Adolf Hitler was appointed Chancellor. Within a year, Hitler and the Nazi party consolidated power. Promising to revive German fortunes, Hitler pursued an aggressive foreign policy to undo Versailles and to make Germany self-sufficient. The idea of Lebensraum (which means “living space”) was to greatly expand German territory in Eastern Europe. Above all else, he opposed what he saw as the threat of Jewish Bolshevism and saw the defeat of the Soviet Union as his destiny.

Hitler’s foreign policy was a series of gambles with increasingly escalating stakes. In 1936, he ordered the reoccupation of the Rhineland, which had been demilitarized by Versailles. The German Army was under orders to withdraw at the first sign of resistance, but none came. That same yea,r the German air force, the Luftwaffe, gained combat experience by supporting the Nationalist side in the Spanish Civil War. Believing the French and the British did not have the stomach for another fight, Hitler’s demands increased. The Anschluss, the joining of Germany and Austria under German rule, took place on March 12, 1938. Hitler then demanded the Sudetenland from Czechoslovakia, a region with 3 million Germans. The British Prime Minister Neville Chamberlain met with Hitler in September 1938 to hash out a peaceful solution to the Sudetenland crisis. An agreement was reached, and Chamberlain claimed he had secured “peace in our time.” Less than six months later, the remainder of the Czech state was annexed by Hitler.

From 1936-1938, Hitler successfully sought out reoccupation efforts, taking possession of the Rhineland, Austria, and the Sudetenland. Still not satisfied, Hitler pressed for yet more territorial concessions and succeeded in claiming Memel from Lithuania in March 1939. Once again, the British and French failed to oppose Hitler’s brazen demands and by the summer, Hitler turned his attention to the port city of Danzig, modern-day Gdansk. In August, to the great surprise of the rest of the world, Germany agreed to a non-aggression pact with the Soviet Union, essentially agreeing to carve up Poland. Danzig was a majority-German territory which had been ceded to Poland by the Treaty of Versailles. Seeking yet another bloodless victory, Hitler demanded the Poles hand over Danzig to reconnect East Prussia with Germany. This ended up being one demand too many and with French and British support, the Poles refused.

The Start of World War II

World War II began on September 1, 1939, when Germany invaded Poland. Hitler’s hopes of keeping the war localized between Germany and Poland were dashed when the British and French declared war on September 3rd. The Poles resisted fiercely but were outmatched by the German army, and a bad situation became worse when the Soviet Union invaded from the east on September 17. Poland fell after a month of fighting, caught in an utterly hopeless strategic position between two hostile powers. The Allies did very little to assist the Poles. Hitler had gambled on a quick victory in Poland and left the German border with France lightly defended. An Allied attack would probably have succeeded but the experience of such catastrophic losses in World War I made the Allies reluctant to go on the offensive. After the fall of Poland, very little fighting took place in Europe in the winter of 1939-40.

The French did not want to fight another war inside France and bear the brunt of the casualties as they had done in World War I. The plan was to do much of the fighting in the Low Countries and to avoid heavy casualties. The British dispatched an army to assist the French, and the expectation from the Allies, and indeed most of the world, was of another long war of attrition. Apparently, the Germans did not get the memo.

Fretting about fighting another lengthy war for which they were not prepared, the German high command spent the winter of 1939-40 trying to find a way to achieve a quick victory. A bold plan devised by Erich von Manstein proposed a surprise attack through the Ardennes forest to cut off the Allied army in Belgium. The plan succeeded beyond even the wildest dreams of the Germans. Believing the area to be impassable, it was the weakest section of the Allied line and no match for the main thrust of the German attack. The Allies were slow to respond and allowed a local setback to become a catastrophic defeat. The British Army narrowly escaped complete annihilation at Dunkirk thanks to a frantic evacuation that whisked over 300,000 soldiers back to Britain in eight days.

With France on the brink of defeat, Italy opportunistically entered the war on June 10, 1940, hoping to gain a share of the German spoils. Two weeks later, the French capitulated and Britain stood alone against the Axis. The English Channel was all that separated the Germans from complete victory; English calls to reach a settled peace were rebuffed by the new Prime Minister, Winston Churchill.

Hitler ordered the Luftwaffe to achieve air superiority over Britain to make an invasion possible, waging an aerial campaign over the skies of England in the summer of 1940. The Royal Air Force was aided enormously by the development of radar technology to detect incoming planes and the bravery of a large number of foreign pilots. In fact, more than 500 pilots from across the world aided Britain during her darkest hour, 400 of which were from Poland, New Zealand, Canada, and Czechoslovakia. Ultimately the RAF prevailed and the German plan for an invasion of Britain was canceled.

Let’s leave Europe for a moment and turn our attention to the war as it played out in the Pacific.

World War II in the Pacific

It’s generally accepted that the German invasion of Poland was the start of World War II, but hostilities had broken out in Asia some years before. The Second Sino-Japanese War began on July 7, 1937 with the Japanese invasion of China.

Japan had fought on the Allied side in World War I, honoring an alliance with Britain. The Japanese experience of the First World War was quite minor compared to the horrific losses endured by the other sides. German territories in Asia and the Pacific were easily seized with few casualties. In the years following the war, the Japanese political landscape altered to a militarized, ultranationalist outlook known as Showa Statism–effectively Japanese fascism.

In 1931 the Japanese invaded Manchuria following the Mukden Incident, an event used as a pretext for the invasion by the Japanese army. In 1937, with tensions running high between China and Japan, a clash between troops near Beijing on July 7 escalated into a full-blown war. The Chinese capital of Nanjing was captured in December 1937 and subjected to a massacre so severe that it continues to place a strain on Sino-Japanese relations to this very day. Despite the losses and large portions of territory taken away, the Chinese refused to give in and the Japanese simply didn’t have the manpower to subdue the entire country by force.

Japan’s diplomatic standing was damaged by the war with China and led to a series of trade restrictions with the United States. In September 1940, Japan signed the Tripartite Pact with Italy and Germany bringing the nations into a loose alliance as the Axis Powers. A lack of natural resources meant that Japan was dependent on foreign trade, primarily from the United States. A failure to reach a settlement saw the US cut Japan off completely in August 1941. A lack of oil was a major problem for the Axis powers and would lead to some disastrous decisions.

Operation Barbossa

Now, back to Europe. Hitler made the fateful decision to break the non-aggression pact with Russia and launched an invasion on June 22, 1941. Hitler believed that after overcoming the Russian forces on the border, the Red Army would crack. He said “we need only kick in the door and the whole rotten structure will come crashing down.” Operation Barbarossa was initially successful; the German army encircled and destroyed several Russian divisions while advancing hundreds of miles. But Hitler had drastically underestimated the lengths the Soviets would go to for survival. 1500 military factories were dismantled and reassembled beyond the Ural Mountains and out of reach of the German military. Workers labored 16 hours a day to dramatically increase war production to previously unimaginable levels. The Red Army suffered enormous losses in men and material but actually grew in size as the war went on. 30 million men would be conscripted by the Red Army from 1941-1945.

The US Enters World War II

1941 was also the year the United States entered the war. The Japanese, believing war with the US was inevitable, tried to gain the upper hand with a preemptive strike against the American fleet at Pearl Harbor. Hoping to cripple the American naval presence in the Pacific and force a settled peace, the Japanese attacked on the morning of December 7. The American fleet lost several ships but crucially, the aircraft carriers and repair facilities were largely undamaged. The Japanese had planned for a decisive naval battle with battleships which ultimately never came. It would be aircraft carriers rather than battleships which would prove the deciding factor in the Pacific.

The United States declared war on Japan and this was met with declarations by Germany and Italy in accordance with the Tripartite Pact. The US agreed to concentrate on Germany first, with about 2/3 of the American war effort being directed to Europe. Much of that effort came in the form of bombing German factories and infrastructure. Unlike the British, the Americans were unwilling to deliberately target German civilians and launched daytime raids in an attempt for greater accuracy. Postwar American studies of strategic bombing showed only moderate success in crippling German industry.

After an invasion of Sicily in 1943 achieved limited success, the Allies finally granted Stalin’s wish of opening up a second front in the west in 1944. Operation Overlord was the largest naval invasion in history. On June 6, known as “D-Day,” troops from America, Britain, Canada, and nine other countries stormed the beaches of Normandy and secured a foothold. By September, most of France had been liberated from Nazi occupation. The Allied forces made steady progress, with some setbacks, in the west while the Soviet forces advanced in the east.

A last-ditch effort by the German army to reverse the tide in the west came in the Battle of the Bulge in December 1944. The counteroffensive failed and though the cause was utterly hopeless, the Germans fought on for another five months. With Berlin about to fall to the advancing Russians, Hitler committed suicide on April 30, 1945. Germany formally surrendered on May 8, 1945, ending the war in Europe.

Japan vs. the US

In the Pacific, the United States adopted a strategy of island-hopping. Rather than try to take everything, the US would invade only the islands on the most direct route to Japan. Naval bombers and submarines wreaked havoc on Japanese shipping lanes, crippling supply lines and preventing much-needed raw materials from reaching Japan. Unlike the Allies in the Atlantic, no serious effort was made by the Japanese to counter submarine raids. By the summer of 1944, the United States had captured Guam and Saipan, providing a base for raids on the Japanese home islands.

While the United States had been reluctant to attack civilians in Europe, no such quarter was given to the Japanese. That the Japanese had struck first led to hardened American attitudes. 120,000 Japanese-American citizens were forcibly interned within the United States from 1942-1945. On March 9 and 10, 1945, American B-29 bombers carried out a massive air raid on Tokyo, killing around 100,000 and destroying one million homes.

With Japan on the brink of collapse in 1945, there was no doubt whatsoever of an Allied victory. For the Japanese, there was no hope of winning but only of forcing favorable peace terms by making an invasion of Japan as costly as possible. In August 1945, Stalin honored his promise to declare war on Japan and the Red Army swiftly crushed the Japanese forces in Manchuria.

The development of nuclear weapons had begun in August of 1942. It was a major research and development project that cost over $2 billion and took three years of dedicated research by many scientists to make a reality.

President Harry Truman ultimately made the decision to use atomic weapons. On the 6th of August, 1945, an atomic bomb codenamed Little Boy was dropped on Hiroshima. Estimates of the number of deaths range from 90,000 to 140,000. Among the dead were about a dozen American prisoners of war. Three days later a second bomb codenamed Fat Man was dropped on Nagasaki, killing up to 80,000. Truman argued that the bombings of Hiroshima and Nagasaki saved thousands, perhaps millions, of Japanese and American lives by making an invasion of Japan unnecessary. It has also been argued that an invasion of Japan could have been avoided anyway if the emperor’s position was guaranteed.

The End of World War II

Regardless, Japan offered to surrender on August 15, 1945. In a rare public address to the people, the Emperor of Japan declared “the war situation has developed not necessarily to Japan’s advantage.” Quite the understatement! The war officially ended on September 2, 1945.

Consequences and Aftermath of the War

The war was not just a clash of armies but of entire societies. The Nazis oversaw the systematic murder of Europe’s Jewish population from 1941-1945. At least six million Jews were killed in German concentration camps. Including other persecuted groups, there were up to 11 million victims of the holocaust.

To field such huge armies, the economies of the major powers were centered on wartime production. Millions of American women supported the war effort; half a million were employed in aircraft production. You’ve probably seen some variation of a Rosie the Riveter poster or magazine cover. The image of a young determined woman declaring “We can do it!” stems from a 1943 issue of the Saturday Evening Post representing the many women who proved they were the equals of men in the workplace. Many American women also served in the armed forces, directly performing a variety of supporting roles. Women of the medical corps braved dangerous conditions to treat wounded soldiers just behind the front lines.

Other marginalized sections of American society also made important contributions to the American war effort. Native Americans had a unique skillset which was used effectively in the Pacific dealing with radio transmissions: The security of these transmissions was vital. If the enemy could intercept and understand a message, they would have a major advantage on the battlefield. With tribal languages almost completely unknown outside of North America, Native Americans were ideal candidates for radio operators. The idea was first contemplated in the final months of the First World War. The American Expeditionary Force was able to maintain the element of surprise during the summer offensives of 1918 in part thanks to the efforts of Choctaw and Cherokee signalmen.

Just like the Germans in 1918, the Japanese were never able to make much sense of the transmissions made by the code talkers. Navajo and other Native American signalmen developed a sophisticated military vocabulary to make rapid and accurate tactical transmissions under extreme conditions. Code talkers participated in every assault made by the Marine Corps in the Pacific from 1942-1945. More than 800 transmissions were sent by Navajo signalmen in the first crucial 48 hours of the American invasion of Iwo Jima in February 1945.

While Native Americans served alongside white soldiers, the same was not true of African American troops; the armed forces did not desegregate until after the war. The most famous African American combat unit of the Second World War was the pilots of the 332nd Fighter Group. Based out of Tuskegee, Alabama, and at a time when Jim Crow laws were enforced in the Southern United States, the Tuskegee airmen overcame racial discrimination to earn the right to fly combat missions. It was believed at the time that African American pilots were inferior to white airmen and not capable of effective leadership. The pilots of the 332nd proved how ill-founded these views were, with an exemplary record of service in World War II.

The 6,000 trucks of the Red Ball Express were primarily driven by African Americans and moved thousands of tons of supplies to the front lines in the summer and fall of 1944. In all, about 1.2 million African Americans contributed to the American war effort, laying the foundations for the desegregation of the armed forces in 1948. This was one of the great contradictions of the United States: fighting against fascist tyranny with a segregated army. Similarly, the British fought for freedom with the resources of a vast colonial empire.

The war brought about many changes, especially in how people saw the world. There are simply too many outcomes to list completely in one video, but some key points are important to note. One of the first priorities for the victorious Allies was to rebuild after years of chaotic destruction. American aid under the Marshall Plan helped the shattered nations of Western Europe to recover. Change was in the air in other parts of the world.

At the end of World War II, about 1/3 of the world’s population was under colonial rule. A period of decolonization took place in the late 1940s and 1950s. To name just a few: India gained independence from Britain in 1947, Indonesia from the Netherlands in 1945, and a very long struggle for freedom began in French Indochina in 1945. To prevent future wars by encouraging peace and international cooperation, the United Nations was founded in 1945.

In the aftermath of the war, the understanding between the United States and the USSR swiftly broke down. Europe became divided as Eastern European countries came under Communist influence. Nowhere was this split more apparent than in the partition of Germany which lasted until 1989. In 1949, the nuclear monopoly enjoyed by the United States ended when the Soviet Union successfully detonated an atomic bomb. Fear and mistrust between the United States and the Soviet Union would not ignite into a full-scale war but would simmer in the decades-long Cold War.


Let’s go through a few review questions to see what you remember:

1. What was the Sudetenland Crisis about?

  1. German territorial claims
  2. German rearmament
  3. The joining of Austria and Germany
  4. None of these


2. Most of the United States’ attention in World War Two was against which country?

  1. Japan
  2. Italy
  3. Russia
  4. Germany


3. The first atomic bomb was dropped on which Japanese city?

  1. Tokyo
  2. Osaka
  3. Hiroshima
  4. Nagasaki


Thanks for watching, and happy studying!


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by Mometrix Test Preparation | Last Updated: December 21, 2023