I've just found an odd option in the editor, it is called "increase army's strength" (or close to that, this is a translation of mine), and it can be found at the bottom right of the 'improvements & wonders' page. It is toggled on for the Military Academy only, and basically it says that armies' attack and defense values are increased by 25%.
Is this true ?
Is it also true that, to compute the armies' attack and defense real values, you add every attack and defense values of the units inside (respectively of course), divide the total by 6, and add the results to the average attack and defense values ? Do both values get down once the army is redlined ?