Is there a trick to destroying the bridge supports at the end of Lizardfolk Chapter 2? I've tried ordering all sorts of captains and Champions to attack a support, but all they do is walk up to it without attacking it. It's preventing me from finishing the chapter, which is really annoying.

No, this is at the end of Chapter 2, entitled "On the Offensive." You have to destroy the bridge to block the Umbragen assault, in order to finish the chapter. Thanks anyway.