Start game as usual, then go to the History Menu and find and select August 6th, 1945 (Hiroshima), and click on the now flashing book in lower right corner to enable cheat mode (this must be done once only). Now use the following hotkeys during gameplay.
W - Win mission
A - Refill ammo
K - Kill visible enemies
L - Lose mission
To enable Hell Cheat Mode, do same as above, but afterwards find and select August 9th, 1945 (Nagasaki) and click again on the now non-flashing book in lower right corner. Hotkeys remains the same.