I'm trying to figure out the nuances of Military Control and Loyalty and their affects on each other.
Capturing a strategic city caused 'Loyalty Checks' throughout the map with higher chances of a favorable outcome toward the capturing side relative to the proximity of the captured strategic city. I also believe that I read that just winning battles will also cause some similar affect, but only for regions with a closer proximity to the battle.
I understand that a 'Loyalty Check' is made each turn in which a region is occupied by units of the side to which the region is not loyal. A random number is seeded between 1-100, if this number is lower than the total 'Police Value' of the occupying units, the loyalty of that region shifts 1%. I believe 1 percentage point is meant. So you would need a huge military force in a region for for a long time to convert the loyalty of that region through military presence alone.
Loyalty has no affect to Military Control in regions not occupied by units. EG: if the USA has 75% Loyalty in a region, but 0% Military Control, there will be no shift in the Military Control until the region is occupied by non-support units of either or both sides not in a passive posture.
However, (and here the rules are vague) if a region loyal to your side (51% or more I guess) is occupied by the other side by forces "without ... enough of a garrison" the "Military Control will gradually shift in your favor and there is a chance that Partisans will appear in the region". If you have 10% or less loyalty in a region with a city the chances of Partisans appearing is even greater.
Also note that if a region is occupied by units of both sides and the units of one side are forced to retreat out of the region, the Military Control of the region will shift drastically to the side still occupying the region. I guess that if the units of both sides are in defensive or passive posture and one side leaves the region voluntarily, this doesn't occur.
Since update 1.14 early cavalry units have the 'NoCapture' attribute, which means that regardless of the size of a force comprised of solely of early cavalry units, they cannot capture (take control) of a city. Depots and harbors can still be captured by these units, however. So early cavalry work a bit like Partisans and Indians.
Early cavalry units do change the Military Control of a region. If you have more than 50% Loyalty in a region with a city controlled by the enemy, can you capture the city with early cavalry as it works with Partisans and Indians? What about raiders?
So it seams that occupying a disloyal-region with too small of a force angers the locals causing the the Military Control of the region to shift against you and risks the locals to organize a militia (an enemy unit is generated) and actually attack you in that region.
Actually fighting a battle in a region scares the locals and Military Control takes a big shift in favor of the winner, though unless the region contains a strategic city, loyalty is not affected.
Have I got this right? Am I missing something?
I'm leaving Martial Law and Suspending Habius Corpus out of the picture, because it has no affect what-so-ever on Military Control other than reducing the chances of Partisans from being generated through occupation by a weak force.