How is the bombard attack working? U have to prepare like on the other attacks to get high% of winning? And if so, when u use Bombard attack, does the prep restarts?

And does it destroy walls or random buildings?

So here is a story to tell of some of the surprises regarding bombard attack:

I march my army to the high walls of Elvaron, proud knights and merciless catapults in huge numbers, to take the town back from the evil orc army of the even more evil Mr. Philosoraptor. My army starts prepping, crafting the ladders, drinking a lot before the battle, the usual stuff. Takes more than 20 days, so no rush there. But my army commander suddenly turns up, and informs me that the catapults are loaded, and ready to bombard the city. Well, I think that sounds fun, it cannot hurt to throw some big stones as well as my own excrement on the monsters hiding behind the walls, can it? Also, probably some walls come down, it might be easier for my knights to charge in town later. So I say, let's do it, bombard.

And the result:

02:30:26 Dec 10th 12 - Khan (Mr. Senki):

Bombard is just like a normal attack its counted form your total prep time and % just like any attack if you attack with it , it restarts the prepping time, and yes it destroys walls and buildings.

More or less we can say that each 100 knights of mine managed to kill 1 gaia! I see some room for improvement.

Yep, but that is not logical at all, and thus really useless. So no point of that being there, whereas if that would mean a bombardment, with a small % let's say max 10% of damage to the defenders, depending on the # of catapults, and some wall destruction, that could be useful. Well, anyway... lesson learned.