Final answer:
The banning of the Korean language and history by the Japanese colonial government is the strongest evidence of Japan's attempts to make Koreans assimilate to Japanese culture.
Step-by-step explanation:
The detail that best supports the thesis that Japan wanted Koreans to assimilate to Japanese culture is "Banned Korean language and history". This action reflects a direct attempt to suppress Korean cultural identity and replace it with Japanese elements, which is a clear indicator of forced assimilation. By banning the native language and history, the Japanese colonial government sought to erase Korean heritage and ensure that future generations of Koreans would identify more with Japanese culture, thereby weakening Korean national identity and making Korea more amenable to Japanese influence and rule.