Fortifications are a category of reinforcements in the World Map. They can be bought for coins in a battle and increase the enemy's effort requirement by a variable amount. Multiple walls can be purchased for one battle and the total effort requirement increase stacks.

There are 4 types of fortifications with increasing costs and effectiveness:

Icon Name Cost
TODO Wooden Palisade 200 coins
Cobbled Rampart 500 coins
Masoned Bulwark 1200 coins
Armored Wall 3000 coins

The effectiveness depends on how many fortifications have already been purchased for this battle, following a curve: Starting mediocre, it quickly rises to huge numbers before falling down again until fortifications are just a waste of money. At the peak of this curve, fortifications are a far more efficient coin investment than troops. Therefore it can be worth it to make an initial investment even when walls are not yet as efficient as troops.

As with all purchases, the most expensive item has the best effect per coin ratio.