Why did the Japanese enter World War 2?

Answer 1

The Japanese were still in the Middle Ages in 1853, when under the guns of a US warship Commodore Perry forced the Japanese to "open" their insular Islands to the rest of the world, for trade. Within fifty years after that the Japanese had steam-powered, all steel armored warships, the equal of any in the world, and rapid-firing field artillery, all the trappings of a modern military, and gave a severe drubbing to the Russians in the Russo-Japanese War of 1905. But coming late to the party, the Japanese missed out on the great colonial grabbing in Asia. The Japanese resented the presence of the European Powers, with their Asian colonies, in the area Japan considered to be her rightful area of dominance, her sphere of influence.

The Japanese joined the Allied side in WWI, not out of any desire to fight for any cause, but as a strategic move to pick up the Pacific Colonies of the German Empire in the Pacific, once Imperial Germany was defeated. This worked out just fine, as Japan was awarded all of Germany's colonies north of the equator in the Pacific at the Versailles Peace Conference. But Japan wanted more. Japan is an island nation, cramped for room, lacking any oil deposits and other Natural Resources. Japanese nationalists, dreaming of their perfect future, came up with the concept of the "Greater East Asia Co-Prosperity Sphere", with Japan as "first among equals" dominating all the other peoples of Asia, after the white men were expelled. It was in pursuit of this dream that Japan embarked on her course of aggressive conquest in 1931, in what many regard as the opening round of WWII, with the invasion of Manchuria. There followed the invasion of China, then the occupation of French Indochina (at the "invitation" of the German puppet state of Vichy France). That last move caused the US to cut off, embargo, the sale of oil to Japan. Having no oil of their own, and only an eighteen months supply on hand, the Japanese had to either knuckle under to US pressure to stop invading their neighbors, cease the aggression, give up the cherished dream of the Greater East Asia Co-Prosperity Sphere, or, find another source of oil. There was plenty of oil in the Dutch East Indies, a colony of the Netherlands, the Netherlands at that moment being occupied by Japan's ally, the Nazi Germans. Japan planned to seize the Netherlands East Indies, but worried about possible US reaction. The Japanese warlords, not understanding that in that long ago time, US presidents could not take the US to war whenever they wanted to do so, worried about the sea lanes between Japan and the Netherlands East Indies being vulnerable to US attacks out of the Philippine Islands. The Philippines were then a US possession, acquired by the Imperialist wing of the Republican Party in the Spanish-American War of 1898. So, to neutralize this threat, the Japanese decided to invade the Philippines, to secure their lines of communication with the Dutch East Indies. Having decided to do that, they also decided to attack the US Pacific Fleet in its anchorage at Pearl Harbor, Hawaii, to remove the possibility that the US would be able to interfere with Japanese plans for this next phase of conquest.