The web page Eurogamer.net had an interview with Jon Hare (Sensible Software). In this interview Jon tells about the development of Cannon Fodder. The original concept of Cannon Fodder was a Rambo style game with a troop element. But at Sensible software they did not make a complete plan before the game development was started. Many of the elements were added when they were making the game. You can read all the details about Cannon Fodder in the interview.