Troops Defending Province with Fortress

[Cosian]

Even if I have a commander with troops set to defend it seems that in a province that has a fortress only the PD defends and I always have to break the siege. Is this correct or am I doing something wrong?

[rdonj]

In order to defend a fortress you have to patrol it.

[Muse]

Even if I have a commander with troops set to defend it seems that in a province that has a fortress only the PD defends and I always have to break the siege. Is this correct or am I doing something wrong?

Troops set to the "Defend" order will defend only the castle--it hints at this in the main order selection list and directly states it in the manual.

To have units guard the entirety of the province, they must be set to the "Patrol" order, if there is a fortress present.

[Knai]

As long as unrest is at 0, they won't kill any population, so its perfectly safe on top of everything else.