Bombarding in the Mountains

[marcuspeddle]

I was fighting the Germans in a hilly and mountainous part of my continent a while ago (we kissed and made up later) and to weaken a horseman that was hanging around one of my cities I rush built a catapult. When my turn came around again I clicked the bombardment button only to find I couldn't fire! The horseman was in range but he was in mountains. I know I need a road to move a catapult through mountains but do I need a road to throw rocks into the mountains? Or do the mountains provide enough cover to protect units?
Thanks in advance for your answers.

[gamma]

Only thing I can think of: was the horseman down to one hit point? If so, you can't bombard it any further.

[marcuspeddle]

I'm not sure if he was in the yellow or in the red but I do know he was wounded. Probably he was in the red and that's why I couldn't attack him with a catapult.
Thanks.