When did World War II begin?
Asking when World War II began is a good way to start a long and passionate debate. Some say it was simply a continuation of the First World War that had theoretically ended in 1918. Others point to 1931, when Japan seized Manchuria from China. Italy’s invasion and defeat of Abyssinia (Ethiopia) in 1935, Adolf Hitler’s re-militarization of Germany’s Rhineland in 1936, the Spanish Civil War (1936–1939), and Germany’s occupation of Czechoslovakia in 1938 are sometimes cited. The two dates most often mentioned as "the beginning of World War II" are July 7, 1937, when the "Marco Polo Bridge Incident" led to a prolonged war between Japan and China, and September 1, 1939, when Germany invaded Poland, which led Britain and France to declare war on Hitler’s Nazi state in retaliation. From the invasion of Poland until the war ended with Japan’s surrender in August 1945, multiple nations were at war with each other, some fighting for the ultimately victorious Allies, some for the Axis.
Origins of World War II
No one historic event can be said to have been the origin of World War II. Japan’s unexpected victory over czarist Russia in the Russo-Japanese War (1904-05) left open the door for Japanese expansion in Asia and the Pacific. The United States U.S. Navy first developed plans in preparation for a naval war with Japan in 1890. War Plan Orange, as it was called, would be updated continually as technology advanced and greatly aided the U.S. during World War II.
The years between the first and second world wars were a time of instability during the worldwide Great Depression that began around 1930. It was also a time when some nations, including Germany, Italy and Japan developed intense nationalist feelings that led to a desire to expand: Germany in Northern and Eastern Europe, Italy in Africa and Greece, and Japan in Asia and the South Pacific. Germany had the added motivation of overturning (and ultimately avenging) the harsh terms forced on it at the conclusion of the First World War.
Competing ideologies further fanned the flames of international tension. The Bolshevik Revolution in czarist Russia during the First World War, followed by the Russian Civil War, had established the Union of Soviet Socialist Republics (USSR), a sprawling communist state. Western republics and capitalists feared the spread of Bolshevism. In some nations, such as Italy, Germany and Romania, ultra-conservative groups rose to power, in part as a reaction against communism.
Germany, Italy and Japan signed agreements of mutual support but, unlike the Allied nations they would face, they never developed a comprehensive or coordinated plan of action.
Initial Moves of the Second World War
On July 7, 1937, a skirmish near the Marco Polo Bridge near Beijing, China, led to open warfare between Japan and China. The outclassed Chinese military traded space for time, steadily withdrawing deeper into the large country to extend Japanese supply lines and hoping to eventually gain assistance from other nations. During the course of the war over 1 million Japanese troops would be engaged in an unsuccessful attempt to subdue China.
The fighting in Europe began on September 1, 1939, when Germany invaded Poland. Previously, Germany, led by Nazi Party leader Adolf Hitler, had annexed Czechoslovakia and Austria without provoking a military response from France or Great Britain. Poland was a step too far; both of those nations declared war on Germany in support of Poland, but they were slow to take effective actions. The French military and government expected Poland would hold out till spring, allowing France time to mobilize. But Germany demonstrated the effectiveness of combined arms warfare, in which infantry, armor, artillery and aircraft work in coordination. This type of war required rapid communication; in preparation, the Germans had developed radios small enough that every vehicle could be equipped with one.