City Attack

When you decide to attack an opponent city. make sure you account the wall.

Because it is 15 defense and 2000 health, you'll want to destroy it as soon as possible. If you don't destroy the wall within 5 rounds (causing a minimum of 400 damage to the wall each round), the attack will be called a draw and you effectively lose.(edited)

Until you destroy it you cannot cause any damage to defending troops and defending long-ranged troops can kill you without fear of losses.

Ideally you will have fast troops that will destroy the wall in the first round, opening it up to your slower troops to actually cause damage to defending troops.

You will most likely lose some troops in the first round, unless the city isn't defended and/or you can destroy the walls and all defending troops before they can retaliate.

The battle field is the same size as you'll find against resource tiles, but the wall goes across the middle. Most non-long-ranged troops will reach the wall in the first round, so there isn't much likelihood that they'll be behind it.