World War II had two primary theaters: the European Theater and the Pacific Theater. The former saw heavy fighting all across the continent, starting with the German conquest of Poland in September 1939.
The West’s war ended with Germany’s unconditional surrender to the Western Allies and the Soviet Union on May 8, 1945.
On the other side of the world, the Pacific Theater was defined mainly by the Empire of Japan’s territories, which covered a large portion of the Pacific Ocean, East Asia, and Southeast Asia.
It saw heavy fighting as far north as the Aleutian Islands in North America and as far south as northern Australia.
Japanese expansion of its territory began much earlier with Manchuria’s invasion, a historical region in China, in 1931.
Imperial Japanese Army (IJA) continued their aggressions largely unchecked with no significant oppositions from other countries.
Approaching the end of 1941, the United States enforced economic sanctions on Japan by cutting off oil exports with the empire.
Japan sent diplomats to Washington to find a workaround to avoid direct conflict between the two countries.
At the same time, Japan secretly deployed warships, including six aircraft carriers for Pearl Harbor, Hawaii, and launched an attack on the U.S. Pacific Fleet on December 7, 1941.
The United States declared war on Japan the following day, beginning much more direct involvement in World War II.
10 Southward Invasion
When World War II broke out in Europe in September 1939, Japan still had not brought the conflict in China to an end despite a series of victorious battles.
Meanwhile, in Europe, the German military force proved to be overwhelmingly powerful for Netherlands and France to cope with.
German victories in Europe encouraged Japan to look southward at the defeated powers’ colonies.
The archipelago of Dutch East Indies (now Indonesia), French Indochina, and British-held Malaya contained oil and rubber essential resources to Japan’s economy.
Control over those regions could make Japan self-sufficient and dominant power in the Pacific.
In contrast to the United States and the Soviet Union, Germany and Italy’s nations recognized Japan as the leading power in the Far East. Germany, Italy, and Japan concluded the recognition with the “Tripartite,” otherwise known as Axis.
Tripartite, signed on September 27, 1940, essentially pledged the signatories to help each other in the event of an attack to any of them by a power not already engaged in a war.
At this point, the United States was not directly engaged in World War II yet. Then things took a sharp turn following the attack on Pearl Harbor by the Japanese.