When I am at peace with my neighbor and I move a stack to attack his city that borders my civ (my cultural boundary extends to his city) and I have seige weapons, I have noticed that when the whole stack is selected, I do not have the bombard option even after I declare war. I have to break the stack, click on a cannon for example, reselct all units and then the bombard option is available. May not be a bug, but definately could use a tweaking.