An Overview of World War II

US troops land on Omaha Beach during D-Day, June 6, 1944. Photograph Courtesy of the National Archives & Records Administration

The bloodiest conflict in history, World War II consumed the globe from 1939 to 1945. World war II was fought predominantly in Europe and across the Pacific and eastern Asia, and pitted the Axis powers of Nazi Germany, Fascist Italy, and Japan against the Allied nations of Great Britain, France, China, the United States, and Soviet Union. While the Axis enjoyed early success, they were gradually beaten back, with both Italy and Germany falling to Allied troops and Japan surrendering after the use of the atomic bomb.

World War II Europe: Causes

Benito Mussolini & Adolf Hitler in 1940. Photograph Courtesy of the National Archives & Records Administration

The seeds of World War II were sown in the Treaty of Versailles which ended World War I. Crippled economically by the terms of the treaty and the Great Depression, Germany embraced the fascist Nazi Party. Led by Adolf Hitler, the rise of the Nazi party mirrored the ascent of Benito Mussolini's fascist government in Italy. Taking total control of the government in 1933, Hitler remilitarized Germany, stressed racial purity, and sought "living space" for the German people. In 1938, he annexed Austria and bullied Britain and France into allowing him to take the Sudetenland region of Czechoslovakia. The following year, Germany signed a non-aggression pact with the Soviet Union and invaded Poland on September 1, beginning the war.

World War II Europe: Blitzkrieg

British and French prisoners in northern France, 1940. Photograph Courtesy of the National Archives & Records Administraiton

Following the invasion of Poland, a period of quiet settled over Europe. Known as the "Phoney War," it was punctuated by the German conquest of Denmark and the invasion of Norway. After defeating the Norwegians, the war moved back to the Continent. In May 1940, the Germans surged into the Low Countries, quickly compelling the Dutch to surrender. Defeating the Allies in Belgium and Northern France, the Germans were able to isolate a large segment of the British Army, causing it to evacuate from Dunkirk. By the end of June, the Germans forced the French to surrender. Standing alone, Britain successfully fended off air attacks that August and September, winning the Battle of Britain and eliminating any chance of German landings.

World War II Europe: The Eastern Front

Soviet troops hoist their flag over the Reichstag in Berlin, 1945. Photograph Source: Public Domain

On June 22, 1941, German armor attacked into the Soviet Union as part of Operation Barbarossa. Through the summer and early fall, German troops scored victory after victory, driving deep into Soviet territory. Only determined Soviet resistance and the onset of winter prevented the Germans from taking Moscow. Over the next year, both sides battled back and forth, with the Germans pushing into the Caucasus and attempting to take Stalingrad. Following a long, bloody battle, the Soviets were victorious and began to push the Germans back all along the front. Driving through the Balkans and Poland, the Red Army pressed the Germans and ultimately invaded into Germany, capturing Berlin in May 1945.

World War II Europe: North Africa, Sicily, and Italy

A US crew checks their Sherman tank after landing at Red Beach 2, Sicily on July 10, 1943. Photograph Courtesy of the US Army

With the fall of France in 1940, the fighting shifted to the Mediterranean. Initially, combat largely occurred at sea and in North Africa between British and Italian forces. Following their ally's lack of progress, German troops entered the theater in early 1941. Through 1941 and 1942, British and Axis forces battled in the sands of Libya and Egypt. In November 1942, US troops landed and aided the British in clearing North Africa. Moving north, Allied forces captured Sicily in August 1943, leading to the fall of Mussolini's regime. The next month, the Allies landed in Italy and began pushing up the peninsula. Battling through numerous defensive lines, they succeeded in conquering much of the country by the war's end.

World War II Europe: The Western Front

US troops land on Omaha Beach during D-Day, June 6, 1944. Photograph Courtesy of the National Archives & Records Administration

Coming ashore in Normandy on June 6, 1944, US and British forces returned to France, opening the western front. After consolidating the beachhead, the Allies broke out, routing the German defenders and sweeping across France. In an attempt to end the war before Christmas, Allied leaders launched Operation Market-Garden, an ambitious plan designed to capture bridges in Holland. While some success was achieved, the plan ultimately failed. In a final attempt to stop the Allied advance, the Germans launched a massive offensive in December 1944, beginning the Battle of the Bulge. After defeating the German thrust, the Allies pressed into Germany forcing its surrender on May 7, 1945.

World War II Pacific: Causes

A Japanese Navy Type 97 Carrier Attack Plane takes off from a carrier as the second wave departs for Pearl Harbor, December 7, 1941. Photograph Courtesy of the National Archives & Records Administration

After World War I, Japan sought expand its colonial empire in Asia. As the military exerted ever control over the government, Japan began a program of expansionism, first occupying Manchuria (1931), and then invading China (1937). Japan prosecuted a brutal war against the Chinese, earning condemnation from the United States and the European powers. In an effort to stop the fighting, the US and Britain imposed iron and oil embargoes against Japan. Needing these materials to continue the war, Japan sought to acquire them through conquest. To eliminate the threat posed by the United States, Japan launched a surprise attack against US fleet at Pearl Harbor on December 7, 1941, as well as against British colonies in the region.

World War II Pacific: The Tide Turns

US Navy SBD dive bombers at the Battle of Midway, June 4, 1942. Photograph Courtesy of the US Naval History & Heritage Command

Following the strike at Pearl Harbor, Japanese forces quickly defeated the British in Malaya and Singapore, as well as seized the Netherlands East Indies. Only in the Philippines did Allied forces hold out, stubbornly defending Bataan and Corregidor for months buying time for their comrades to regroup. With the fall of the Philippines in May 1942, the Japanese sought to conquer New Guinea, but were blocked by the US Navy at the Battle of the Coral Sea. A month later, US forces won a stunning victory at Midway, sinking four Japanese carriers. The victory stopped Japanese expansion and allowed the Allies to go on the offensive. Landing at Guadalcanal on August 7, 1942, Allied forces fought a brutal six-month battle to secure the island.

World War II Pacific: New Guinea, Burma, & China

A Chindit column in Burma, 1943. Photograph Source: Public Domain

As Allied forces were moving through the Central Pacific, others were desperately fighting in New Guinea, Burma, and China. Following the Allied victory at Coral Sea, Gen. Douglas MacArthur led Australian and US troops on a lengthy campaign to expel Japanese forces from northeastern New Guinea. To the west, the British were driven out of Burma and back to the Indian frontier. Over the next three years, they fought a brutal battle to retake the Southeast Asian nation. In China, World War II became a continuation of the Second Sino-Japanese War which had begun in 1937. Supplied by the Allies, Chiang Kai-Shek fought the Japanese while warily cooperating with Mao Zedong's Chinese Communists.

World War II Pacific: Island Hopping to Victory

Amphibious tractors (LVT) head for landing beaches on Iwo Jima, circa February 19, 1945. Photograph Courtesy of the US Naval History & Heritage Command

Building on their success at Guadalcanal, Allied leaders began advancing from island to island as they sought to close on Japan. This strategy of island hopping allowed them to bypass Japanese strong points, while securing bases across the Pacific. Moving from the Gilberts and Marshalls to the Marianas, US forces acquired airbases from which they could bomb Japan. In late 1944, Allied troops under General Douglas MacArthur returned to the Philippines and Japanese naval forces were decisively defeated at the Battle of Leyte Gulf. Following the capture of Iwo Jima and Okinawa, the Allies opted to drop the atom bomb on Hiroshima and Nagasaki rather than attempt an invasion of Japan.

World War II: Conferences & Aftermath

Churchill, Roosevelt, & Stalin at the Yalta Conference, February 1945. Photograph Source: Public Domain

The most transformative conflict in history, World War II impacted the entire globe and set the stage for the Cold War. As World War II raged, the leaders of the Allies met several times to direct the course of the fighting and to begin planning for the postwar world. With the defeat of Germany and Japan, their plans were put into action as both nations were occupied and a new international order took shape. As tensions grew between East and West, Europe was divided and a new conflict, the Cold War, began. As a result, the final treaties ending World War II were not signed until forty-five years later.

World War II: Battles

US Marines rest in the field on Guadalcanal, circa August-December 1942. Photograph Courtesy of the US Naval History & Heritage Command

The battles of the World War II were fought across the globe from the fields of Western Europe and the Russian plains to the China and the waters of the Pacific. Beginning in 1939, these battles caused massive destruction and loss of life and elevated to prominence places that had previously been unknown. As a result, names such as Stalingrad, Bastogne, Guadalcanal, and Iwo Jima became eternally entwined with images of sacrifice, bloodshed, and heroism. The most costly and far-reaching conflict in history, World War II saw an unprecedented number of engagements as the Axis and Allies sought to achieve victory. During World War II, between 22 and 26 million men were killed in battle as each side fought for their chosen cause.

World War II: Weapons

LB (Little Boy) unit on trailer cradle in pit. [Note bomb bay door in upper right-hand corner.] , 08/1945. Photograph Courtesy of the National Archives & Records Administration

It is often said that few things advance technology and innovation as quickly as war. World War II was no different as each side worked tirelessly to develop more advanced and powerful weapons. During the course of the fighting, the Axis and Allies created increasingly more advanced aircraft which culminated in the world's first jet fighter, the Messerschmitt Me262. On the ground, highly effective tanks such as the Panther and T-34 came to rule the battlefield, while at sea equipment such as sonar helped negate the U-boat threat while aircraft carriers came to rule the waves. Perhaps most significantly, the United States became the first to develop nuclear weapons in the form of the Little Boy bomb which was dropped on Hiroshima.

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Hickman, Kennedy. "An Overview of World War II." ThoughtCo, Apr. 5, 2023, Hickman, Kennedy. (2023, April 5). An Overview of World War II. Retrieved from Hickman, Kennedy. "An Overview of World War II." ThoughtCo. (accessed June 2, 2023).