Letting you know that contrary to the rest of the Panzer Campaigns series in the Japan '45 game a Field is a rice paddy (see the 3D terrain image for it). Some folks are noting that their Motorized unit types (HQs, engineers, recon infantry) cannot enter a Field hex. This has to do with the fact that while normally during this time period in Japan the weather is dry, Glenn Saunders did an exhaustive check of the weather and found it to be very moist for 1945. See the Programmed Weather file (weather.dat) or look in the game using the Programmed Weather rule and check the weather info.
Thus Motorized units cannot enter a Field hex because the rice paddies had not dried out and also many of the rice paddies were terraced. This makes movement difficult at times especially at Ariake Bay and in the Miyazaki - Eastern Beaches area.
There is always a way to move the unit around the rice paddy. If for some reason you cannot find a path post the hex(es) in question and I will look over the map for you.