I’ve read in numerous books that Kuomintang made money from opium and that the Golden Triangle in Southeast Asia after the war was set up by the nationalists. How much is known about their selling drugs?
The KMT and the communists both grew and sold opium during the war. For the KMT, it was a regional thing. Starting from the founding of the Republic in 1911, there were national, provincial, and municipal opium control boards that were supposed to regulate and reduce the opium trade, but very often just became cash cows for whoever was in charge. (not at the national level, but in a lot of provinces) British Malaya and French Indochina and Japanese Taiwan also had similar organizations. The British one actually did good work on reducing opium, while the French one just used it to fund the colony.
The communists, meanwhile, had an explicit policy of growing opium and selling it in the White areas during the war as a way to fund their armies.
After the war, the KMT would tell its troops stationed in North Burma to self fund via the drug trade, but that was a post civil war thing. It wasn’t policy during WW2.