Throughout the entire movie, all the Japanese soldiers are using British rifles and machine guns.

The Japanese soldiers are all using British Lee Enfield rifles, and the machine gun used from the back of the lorry truck is a British made Vickers belt-fed machine gun.

The Japanese army during WW-II used Arisaka rifles, much different to the ones in the movie.

Once you know what to look for, very easy to spot.

British rifles are used by the Japanese soldiers during the entire movie.