Press Delete during play in 3D mode and enter the following: 

BANNOCKBURN             Kill all enemies
BASTILLE DAY            All walls breached
BUCKS FIZZ              All troops retreat
DRESDEN                 All buildings on fire
HAEMORRHAGE             No blood
KILLCAM                 Kill camera
SESQUIPIDILIAN          AI cheats enabled
STEVE REEVES            All troops harder to kill
THE FIVE HUNDRED        Kill your own troops