Laying siege to a province requires a certain size army - at least as big as the garrison in the fort you are attacking. As attrition wipes out your forces (and in northern Europe, the winters will kill a lot) they will either guard the fort (no cannon, but they'll stand there) or they will pull out (the morale gets too low and they can't sustain the siege).
The red x you see means a) that the force is insufficient to guard the fort. Make the army bigger. b) there is no route there, try an alternate one.
A retreating army has very low morale and can get easily beaten by even token forces. It takes months before the morale will increase.
Your best bet as Russia is to churn out lots of infantry (very cheap for Russia) and assault the forts instead of waiting out a siege. Your supply level is weak in foreign land and winter will kill more than the assaults on the walls will.
Porcius
The red x you see means a) that the force is insufficient to guard the fort. Make the army bigger. b) there is no route there, try an alternate one.
A retreating army has very low morale and can get easily beaten by even token forces. It takes months before the morale will increase.
Your best bet as Russia is to churn out lots of infantry (very cheap for Russia) and assault the forts instead of waiting out a siege. Your supply level is weak in foreign land and winter will kill more than the assaults on the walls will.
Porcius