Consequences to using nuclear weapons?

Nukes can cause good damage to an army in any terrain. If you have units together and are facing a rival armed with nukes, then separating your units from each other can reduce nuclear damage since nuclear damage has approx 2-3 tile radius. Nukes could kill renaissance and maybe modern era units in one shot. Later units could barely survive an attack with little hp left. Nuking cities halves the city population if theres no bomb shelters and plunders nearby improvements with fallout.