Japan started its military drive when pressure groups wanted Japan to invade Manchuria. The government did not want this, but political extremists managed to infiltrate the garrisons stationed in and around manchuria and pursuaded the commanders to attack. The Japanese did so, and, as there was little resistance, easily conquered it.
Seeing the ease of such a gain, the Japanese wanted more. The government was bvehind this venture, and engineered an incident in which the Chinese appeared to open unprovoked fire on the Japanese. Without waiting for a Chinese explanation, the Japanese commenced hostilities. In a few weeks they had overrun most of northern China and captured Peking. The Japanese were guilty of murdering 200 000 Chinese in cold blood - this was the start of their going off the rails.
Japan became more Nazi in outlook. There were the equivalent of Orwellian Thought Police and there were military personnel everywhere. Military training started at primary school, and no school was without an instructor. Western customs were discouraged by the police and there was an extreme military emphasis on everything. It was almost a police state. The glory of war was stressed.
The country and its commanders wanted out of the military operations by 1940 (they were not in the war yet). Because of the de-emphasis of Western ways, the Japanese were less Allied and more pro-Axis. When Hitler had a string of successes in France, Japan was encouraged to resume her military stance and was soon occupying French Indo-China.
The Japanese Navy was very strong and won many victories. The U.S. was nervous about this and so embargoed oil - the navy was caught short and was doomed (!) if it could not get more. Most of the Dutch East Indies were oil-rich, and so Japan decided to invade them; the only problem was how to get the supplies back to Japan without interception and attack from either the U.S. Pacific Fleet or British Royal Navy. Japan decided that the U.S. fleet was much more of a treat, and decided to attack it; this was the cause of the attack on Pearl Harbour. The Japanese Navy sailed 4000 kilometres without being detected, coming with 200km of the base in Hawaii. Here they were still not detected and decided to attack on Sunday the 7th of December 1941. This they did, and when the planes were detected on radar the U.S. commanders dismissed the blip and ignored it. They japanese came in and sunk all nine battleships, several cruisers and several destroyers.
The Japanese nation was drunk with success and pressed on. They determined that they wanted Malaya - here they were outnumbered 2 to 1. However, they attacked anyway and this was in their favour - the English were bureaucratic and their army was simply not as good as the Japanese one. The Japanese used bikes to get to the font and keep advancing, as the roads were pretty terrible. The English did not; they still thought the island could hold out for 3 months. This did not occur, as it took 7 weeks for the Japanese to advance the 600kms. On September the 15th 1942 the English and Australians surrendered - 130 000 troops were taken prisoner.