Yea, USRanger, mostly Burma. 
BrownBaron: That's why I stated Zekes inSTEAD of Oscars. The Japanese Army fought the RAF and later, the USAAF in the CBI using Ki-43 'Oscars' and Ki-44 'Tojos'. In fact the the Ki-43 was Japan's most significant aircraft in terms of number of planes built, yet we lack it in-game. 
Spitfire V's fought until early '44 when Spitfire VIII's arrived in-theatre. 
One of the more famous engagements of RAF vs. JAAF aircraft happened from 6th-23rd of Feb. '44 when the Japanese sent hundreds of fighters and soldiers to attack General Slim's 14th army in Arakan, around the India-Burma border as a final attempt to get to India. The British were besieged but C-47 Dakotas (and C-46 Commandos) managed to drop them ammo, food and supplies thanks to the protection of Spitfire pilots. 
A Forgotten War indeed  

EDIT: Spelling