Real price of fortified region is 4 PP. You have 16PP only because it is the first month of the war. After it will be reduced to 8PP, then 4PP.
Fortified region allow you to built in advance fortification to better fort level. (See manual about it).
Careful fortified region do not built much alone, you need to assign to it sappers or construction units.
They have bad combat value you may want to disband them before enemy contact.
Currently there's a bug in the game that allows L2 forts everywhere on the map. After next patch the rules will be as listed in the manual:
Fort level 5 can be built only in cities with large port containing a fort unit.
Fort level 4 can be built only in big cities (city, light urban or heavy urban terrain) or towns with port containing a fort unit.
Fort level 3 can be built only in big cities, towns with port, in hexes with a fort unit or adjacent to an enemy.
Fort level 2 can be built only next to a fort unit, in coastal zones or up to 3 hexes from a supplied enemy unit.
Fort level 1 can be built only up to 20 hexes from a supplied enemy unit.
In swamp terrain the fort cannot be larger than 2.
The highlight being here that in an open area, a fortified zone allows L3 on one hex and L2 in the surrounding hexes, which is a big improvement over plain L1 forts.
Make sure you attach experienced construction or engineer units to the forts, that way they dig a lot faster. When defending, you can also attach combat SUs to them, and they will get automatically committed to defensive battles. There's also a special bonus for artillery attached to fort units:
To better simulate the ability to pre-register fire locations, the effectiveness of artillery fire is related to the fort level of the hex containing the firing artillery. The higher the fort level, the more effective artillery in that hex will be in combat.
Due to their ability to participate in multiple battles, artillery support units attached to headquarters units do not receive any benefit from fort levels when committed to combat, so this benefit is limited to artillery combat units as well as artillery support units directly attached to fortified units.
< Message edited by Nix77 -- 9/19/2017 3:41:29 PM >