I didnt engage in any siege battles myself, but I had just made a rather smashing army ( As Prussia, 4 life guards, 2 grenadiers, 4x 24pnd cannons, 2x 24pnd howitzers, 4 light infantry, 3 horse guards) and sent it to take Poland (owned by austria) which was completely ungarrissoned, so it was a battle between me and armed mobs, I hit the surrender button, and they surrendered! so I took it without a fight.