In the section on campaigns:
Example: You invade France using the Holy Roman Empire campaign op. The HRE has two knights (red and white, but their color does not matter in a campaign), so you must pay two florins. Note you are disallowed to invade with just one knight for economy. Since France has no Ruling Class, the[/quote]re are no defenders....
This is the only place that I could find in the manual that mentions this. So is this a universal rule - you always need more than one knight to campaign?