If your hero / army is in a city that is besieged you can only fight the enemy if he attacks, yes?



Otherwise you're stuck in the city?



Doesn't it make more sense to have your army outside where you can attack?



Or is there some benefit to being in the city I'm missing?

If your army is outside the city, it will enter as reserves to militia + governor.



If your army is on the city, it can attack the besieging army (if it has path, but weird cliffs + districts might prevent this)



If your army is inside the city, it costs less upkeep and can be created on the city even if the city is under siege (then see "on the city" above); not sure how it works with milita/reserves, you tend to get the full army, then militia entering as reinforcements, which is ideal; don't know how it interacts with governor capacities



My best move for essential cities (capital) is to keep army in city + additional army to enter via reserves. For non-essential cities, I keep army outside of city-- I don't care if I lose the city for 1 turn, I will counterattack rather than enter via reserves usually.