We need to go all the way back to the 1850s to answer this one as you see young padawan, before 1852 Japan was an isolationist country. Sure, there was some trade with the Dutch, but it was limited to Nagasaki. That all changed in 1853 when Commodore Matthew C. Perry of the United States Navy steamed into what is now Tokyo Bay to deliver a letter from U.S. President Fillmore to the ruler of Japan at the time, the Shogun. The Japanese told informed Commodore Perry to kick rocks and go to Nagasaki like everyone else, which he ignored and lead to him being surrounded by the Japanese Fleet. The Commodore responded by shelling the harbor until they agreed to take delivery of the letter. Perry came back a year later and forced the Japanese to sign the Convention of Kanagawa, which opened the ports of Shimoda and Hakodate to American trade.

The terms were dictated by the Americans as the Japanese were in no position to resist. And that, my dear Reditter is where modern Japanese history begins. Perry’s missions to the country shattered the illusions the Japanese had that their country was a strong one. Japan’s isolation allowed the Japanese to think that they might escape the fate the Chinese were suffering – that idea was destroyed.

You have to understand, the Japanese of the day were absolutely terrified that they’d end up like China – so drastic changes and reforms were undertaken in 1868 – the Meiji Restoration; the Shogun was stripped of power which was placed in the hands of the Emperor’s advisors and the country started to industrialize.

Japan was now playing catch up with the West, else risk being subjugated by them much like China. Western clothes and fashion were adopted, the military was recreated along Western doctrines, a parliament was created, etc. Now, in the 19th century a country had to engage in imperialism else it will be made to look weak – the closest and easiest target was Korea. In the 1890s Korea was a liability for Japan, not because the Korean nation was strong, but because it was weak. The Japanese were worried that a Western nation would invade Korea and use it as a staging ground to invade Japan. This line of thinking along with the fact the Korea is rich in natural resources and Japan is not led to the decision to invade.

The problem with invading Korea was that it was a tributary state to China and free of Japanese presence. Opportunity presented itself in 1894 when China sent troops to Korea to put down a rebellion, this prompted Japan to send troops as well – China got stomped by the Japanese Army. This led to the signing of the Treaty of Shimonoseki; Korea became a tribute state to Japan, Taiwan became a Japanese colony and the Japanese gained the rights to several Chinese cities.

These gains started a rivalry between Japan and Russia for influence in both Korea and Manchuria which resulted in the 1904-05 Russo-Japanese War, which the Japanese won. Japan officially made Korea a protectorate in 1905 and was later annexed in 1910.

Japan was now seen as a World Power but was viewed as a rouge state and didn’t have many – if any - allies.

From 1926 to 1928 the Chinese government embarked on the Northern Expedition, bringing the country under the control of the Nationalist Government based in the city of Nanjing. By 1928 China was a much stronger nation than it previously was. The Japanese viewed the resurgence in China as a threat to their holdings in Manchuria and Korea. The idea of losing anything to China was unacceptable as they had spent the last 50 years trying to avoid being like China. So, in 1931 the Japanese invaded Manchuria and by 1937 Japan was in a full-scale war with China. This put a tremendous strain on the Japanese economy and resources – and there were only two places to look for more: Siberia and the South Pacific and in the end it was decided that the South Pacific was the course to be taken – resulting in Pearl Harbor.

In summary: Japan didn’t help these countries because Japan didn’t want to be these countries. It was either colonize or be colonized.

Hey there,

Just to let you know, your question is fine, and we're letting it stand. However, you should be aware that questions framed as 'Why didn't X do Y' relatively often don't get an answer that meets our standards (in our experience as moderators). There are a few reasons for this. Firstly, it often can be difficult to prove the counterfactual: historians know much more about what happened than what might have happened. Secondly, 'why didn't X do Y' questions are sometimes phrased in an ahistorical way. It's worth remembering that people in the past couldn't see into the future, and they generally didn't have all the information we now have about their situations; things that look obvious now didn't necessarily look that way at the time.

If you end up not getting a response after a day or two, consider asking a new question focusing instead on why what happened did happen (rather than why what didn't happen didn't happen) - this kind of question is more likely to get a response in our experience. Hope this helps!