To be honest, I have no idea if this is normal or not, but since the game is online and I can do anything else just by initiating a command, do I need to be connected on that hero continuously until the attack is finalised?
I tried twice to attack someone, I connected then to my other hero, when I came back my troops were back in the town and the fight never took place. If it's not a bug a requirement like that is just stupid.