Re-using ladders?

[Lord Condormanius]

i am under seige by the Spanish. After they penetrated my first line of defense, I retreated to the second circle. They tried to bring their rams to my second gate, but my ballista towers tore them apart. i thought I was home free. The Spanish have used all of their seige equipment.

...then I almost had a heart attack when I saw them take their ladders down and carry them inside my castle. I gues you can do this now... or at least the Spanish AI knows how.

[Flavius Gonzo]

You can do it too -- select a unit and have them click at the base of a ladder that has been used and is propped up against a wall.

[Nestor]

Actually I survived the Mongols just because they didn't know how to reuse their siege equipment. My lone general and three HA (soldiers, not units) staring at the amazing scene of some 2000 Mongols that didn't know how to attack the inner castle (they had a couple of ladders and their rocket things).

There has to be some randomness in this or else I can't explain why sometimes the AI doesn't do it.

[Oaty]

When it is more than one stack they do funny things like steal siege equipment off of other armies, only to be marching them in front of towers to get lit on fire. Instead they'd be smarter to reenforce the assaulting side, if only armies that didnt have siege equipment came on as reenforcments on the same side as the assaulting army.