Ballista

[colossk]

I have a question about Ballista's. I understand that If I use them to attack I can target an enemy building. Will sending them destroy a level 15 building go from 15-zero in 1 shot or will it take several attempts to do so?
For example, If I send 100 rams to take down a wall usually a level 14-15 wall is taken to zero instantly, is it the same with ballistas?

Can I send these by themselves or must they go with an attack force?

[Boomhaur]

You can send them by them selves. It all depends on how many you send. The city will defend agaist them. Use the troop simulator so you can sent enough of them they are slow moving.

[Blitzcraig]

When sending ballistas by themselves make sure there is no troops in the city you are attacking. It works better.