Greater East Asia Co-Prosperity Sphere
Capturing European Controlled Asian Territories under Veil of Co-Prosperity
Map showing Japanese occupied areas of the Greater East Asia Co-Prosperity Sphere. US Army photo.
After WWI, Japan was awarded the German colonies in Korea and the Marshall Islands, and then they also had railroad rights in Manchuria. However, the Japanese were intent on capturing more possessions in Asia for several reasons.
One reason is that Japan is an island with a large population and very little resources of their own. But the other part was that they were emulating the European Empires, particularly the British Empire with so many possessions in Asia.
Asia for Asians
Japan frequently referred to their expansionist program as the creation of a Greater East Asia Co-Prosperity Sphere, and along with that went the phrase "Asia for the Asians". It was meant to portray a vision of Japan leading Asian nations in looking out for Asia. But I think most of the Japanese thought of it more as just a pleasant phrase and what it really meant was that they would simply displace the European masters, and claim all of these Asian colonies for the benefit of Japan.
Additional Resources Needed by Japan
Japanese stamp showing the Greater East Asia Co-Prosperity Sphere. Public domain photo.
In order to have an industrialized county, you need things like iron ore and coal, oil, and rubber for tires, chrome, tin for tin cans and to weatherproof iron and steel. So there were all those resources that all the western countries competed for to support a mechanized society. Manchuria had iron and coal mines that the Japanese exploited heavily throughout WWII. Indonesia had oil, rubber and tin - then it was called the Dutch East Indies because it was a colony of Holland. So everything else were extra people, extra labor, extra food sources. China had a lot of rice growing areas and lots of people to put to work.
In addition, some of the areas Japan wanted to capture had strategic value in that they would be places where airstrips could be built, or places to locate troops to defend other areas that they had captured. Ultimately that's why the Japanese wound up attacking the Philippines because the sea lanes from Japan down to Indonesia went right past the Philippines. It was a place where the Americans could attack the Japanese shipping and the Japanese fleet as they shuttled back and forth between Indonesia which had the oil, rubber and tin, and the homeland island. Formosa, Taiwan, was within bombing distance of Manila, and vise versa, Manila could have bombed Formosa. They could have bombed Hong Kong as well and you could cover the entire strait that had to be traversed to get to Japan if you were starting in Indonesia.
Continuing their expansionist goals in 1931, Japan blew up a little section of railroad track and claimed it was a Chinese attack upon the Japanese interests. The Japanese army proceeded to invade Manchuria, and make it a Japanese colony with a little puppet government named Manchukuo.
Japanese Expansionism & War with China
Japanese occupied Peiking (Beijing). Public domain photo.
In 1937, the Marco Polo Bridge Incident occurred which basically touched off the Sino-Japanese War. The Japanese took Peiking (Beijing), and proceeded to invade other cities along the coast of China, eventually working their way into Nanking, which was the first major inland city that the Japanese captured. That incident became famous in the Western newspapers as the Rape of Nanking (Nanking Massacre), where, after the city fell, and the Chinese soldiers withdrew, the Japanese soldiers proceeded to loot rob, rape and kill ordinary unarmed Chinese civilians.
Co-Prosperity - a Euphemism for Japan's Attempt to Control East Asia
Essentially, China was in WWII fighting Japan beginning in 1937, and continued to resist as Japan attempted to create an Asian empire headed by the Japanese, under the guise of Co-Prosperity. Japan, and China continued fighting until the end of WWII.
So the Co-Prosperity Sphere proved to be a Euphemism for Japan's attempt to control East Asia, rather than an effort to abolish Western colonialism in Asia, and promote the interests of all countries encompassed by the East Asian Sphere.