[Rule 3.1 Action Segments]

[campsawyer]

A valid move. Probably have used this before, but the resolution of the fire was not very interesting so it wasn't remembered. With your example it is only a 8 column shot on the BF table, best you can do is a morale check. It might be more interesting if this was a subordinated activation where the leader activating the mortar also actives a stack to assault after the mortar attack. This could prove very useful it the mortar disrupts or demoralizes the target and then the assault can get an advantage.