There were openings where tanks couldn't reach. Those did require infantry assaults. Artillery was always available to the troops; however, plunging fire wouldn't go into the openings.
Daisy cutters are today's answer to caves; and, they are way too big for cannons. Air power is the most effective weapon by a long shot.
I like the description of the FAE bombs near the caves... It would create a vacuum that would suck the air out of the cave with incredible force, and everything in the cave with it.
That would be fun to watch.