The essence of Engle Matrix Games is that they allow you to do whatever you want to, so long as you can make a logical argument. You play a leading general of the period. Each turn you get to make one argument/order about what you want to happen that turn. You can make arguments for your side, to cause problems for the other side, or to change the rules! (No more than one level of rule change.)
This is a list of the campaign rules (and one day multi-player games) scattered around my site.