Once a coastal Fort is conquered, seems as if it changes its loyalty 100% towards the USA. However, once reconquered this doesnt change, so acts as a powerful "RADAR" without reason.
Some example
Once USA captures a fort, usually loyalty changes to a full 100%, (that is OK for me in fact, as the fort is just a small fort, not a full region)...
However, once reconquered, loyalty still holds USA 100%, acting as a detection post without reason. It should re-change loyalty 100% to CSA
The trick
can be due to the fort being destroyed before the "reconquer", perhaps there is some event fired depending upon the conquest of a fort, not of an area.
However, once CSA captures Ft Sumter, I ve checked in some games it changes loyalty to a CSA-100%, but sometimes it doesnt. In case not, this is a help for the USA... mmmh Perhaps some of the CSA soldiers in the fort is acting as a spy
for the federals of course...
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. I ll check my old saves to check why my garrisons didnt achieved to change loyalty, perhaps it was my fault not achieving military control enough.