In Manchukuo
After graduating third in the class of 1944, Park was commissioned as a lieutenant into the Imperial Army of Manchukuo, a Japanese puppet-state, and served during the final stages of World War II as aide-de-camp to a regimental commander. He changed his name again from Takagi Masao to Okamoto Minoru (岡本実) in order to engage in intelligence activities against Korean guerrillas operating in the region. The Japanese used Korean turncoats to suppress Korean armed resistance.