There were alot of warlords during that period and they each had thier own fight to fight. Usually against each other. They were very uneducated also. Countries would send aircraft to them and they would bury them for safe keeping.
There also alot of opium use and that may have caused them to be kind of mellow toward making war. Usually the port cities.
Also they had a caste system like India and that made it hard to get anything done. The leaders were very poorly trained but if they were in the upper caste then they led and the underlings followed.
Lack of supplies is anouther reason. The China Burma theater was at the bottom of the list in the supply chain for both the British and Amercians.

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