How does attrition work
I recently made a helicopter gunship and it said I could position it over mountains. So, I moved it onto one of my mountains. A few turns later, my gunship dies of attrition.
How does this happen - How does attrition work?
I was not at war with anyone at this time, and it would have alerted me if there was a barbarian (i'm not even sure if there are barbarians anymore).
Helicopter Gunships receive damage if kept on a mountain tile. They state this in their informational view.