-ian code

[Monk]

Quoted from Frogbeastegg's Beginner's Guide to MTW in the "guides" section of the forum.

-ian - debug mode, runs in a smaller screen, you can move the camera about more in the battle maps to get close up views, you can disable the AI or switch factions using the number keys. The A key allows you to put the game on auto run.

Switching factions is done using the 0-9 keys on your keyboard, also using shift+0-9 will let you access more factions. i don't remember any other keys, but by experimenting a bit you'll find all it's uses.

and here's how to activate this code (and indeed any command line in mtw). again quoted from Froggy's guide...

These are not exactly cheats; instead you add them to your MTW or VI shortcut. Right click on your shortcut, and then choose properties. In the target box you should see something like:
F:\Program Files\Total War\Medieval - Total War\Medieval_TW.exe
if you have plain MTW or
F:\Program Files\Total War\Medieval - Total War\Medieval_TW.exe -strictserver
if you have both MTW and VI. To add a shortcut you must leave one space after the mark, then enter the command line. To use multiple command lines just leave a space between each one and remember to include the - at the start of each successive line. Choose to save your changes and exit the properties box. Then start the game with the shortcut.