Assault with Cavalry

[Narwhal]

Hi there,

I have a situation in my game versus Loki100, on which my decision lays on arcane rules.

My cavalry corps has Troppau under siege, and thanks to siege guns they just "borrowed" from some Austrians, has even breached it. There are no other Prussians to support, and according to the reports of my scouts, an Austrian army might be on its way. I have a window of opportunity of one, maybe two turns.

A small Austrian corps hid inside Troppau, so even with a strong cavalry corps, victory is not certain in assault.

When a fort is breached, the text says "this wall brings no more defensive bonus". Does it mean my cavalry fights like it would on the relevant terrain, or does that mean I fight like I would in a fort, i.e. with cavalry at 10% ATK fire and - 1 in ATK TQ, which would be a "no go" for me ?

Thank you.