The idea of the Co-Prosperity Sphere was announced by Prime Minister Matsuoka Yôsuke in August 1940, but went back many years. Leaders in Japan - then, as now, the richest country in the region - had long been interested in the idea, partly to extend Japanese power and partly to free Asia from being colonies of European countries.
As part of its war drive, Japanese leaders spoke of "Asia for Asians" and the need to liberate Asia countries from imperialist powers. In some cases they were welcomed when they invaded neighboring countries, driving out the British and French armies. In general, however, subsequent brutality and the hardship of war led to the Japanese being regarded as little different from Western occupiers. The Co-Prosperity Sphere collapsed with Japan's defeat.
See also: Imperialism in Asia