The manual is unclear with regards the interaction between fortified zones and forts, although it is detailed on the mechanics of fort construction once they exist.
My vague understanding is demonstrated by these thoughts! :-
It seems that the normal way a player can instigate the construction of a new fort is by using Shift-F and expending 4 APs to place a fortified zone in a hex provided they also place a combat unit in the hex? Is construction of new Forts started in any other way?
There are a fortification zone(FZ, many also just call em forts for short). Then there are fort levels. The first as u indicate functions just like any other unit. U place it as inidcated above. It counts for a unit stacking wise, it starts with 1% ToE and with refit on and draws replacement like any other unit, u can attach SU and so on. Only difference is that is has 0 MP cant move and therefor cant retreat if such a result occures in its hex, In that case it surrender with any men/equipement in it.
Then there are fort levels. Those arent a unit, but an CV modifier that a hex can obtain. So these 2 thigns are seperate tho FZ have an effect directly and indirectly on fort levels but ill come back to that.
I gather u read the old manual. If but u hafta do it manually go into the manual folder of the game there is a file called WITE-manual-us_letters.pdf. Its an updated manual and lots of thing has changed in game since the original manual was released. The original manaul is of limited value now a days. The updated manual has under each paragraph inserted in red tex what ever pacthes affects that rule. among others lots of stuff relating to FZ and fort levels. Remember to thx Apollo/Leo for ther work when u see him.
Fort levels are build by having any unit in a hex(including but not excluded to FZs, remember it acts like a any other unit). If the unit have MP left at end of a turn a unit will use the remaning MP/time to build fort levels. How good a unit is at this u can check in the unit menu by checking its Construction value. The higher the better. In effect some will have such a low value u wont see them build much. Also there is a direct corrololation with amount of MP non used and digging/bulding ability. The less % of starting MPs u have left the less or no build is done.
There are some limitations on fort levels tho. U can obtain max fort level 2, less:
Requirement to build up to Fort Level 5 - Only will be built in port hexes that have a fort unit(FZ). Once built, the fort unit(FZ) is not needed to keep the level 4 fort. Not possible in a swamp hex.
Requirement to build up to Fort Level 4 - Must have a fort unit(FZ) in the hex. Once built, the fort unit(FZ) is not needed to keep the level 4 fort. Not possible in swamp hex.
Requirement to build up to Fort Level 3 - Must be adjacent to an enemy hex, be an urban or city hex, or be in or adjacent to a fort unit(FZ).
So apart from frontlines hex or city/urban hex. U need a FZ in or adjecent to get higher than fort levels 2. Thats how they interact. Apart from FZ has a low Construction value so it in it self just like any other unit can also build tho slowly in them self. As FZ is a unit it can counteract fort level decay from happining, less its really low in ToE. Any combat unit will stop decay, it doesnt have to be a FZ. Non combat unit wont stop but slow decay.
Decay rules has been changed too so now u need a fort level of 4 or higher to avoid decay or have a unit in the hex to stop the decay.
SUs can be attached directly to a FZ (or to a combat unit in a FZ) to improve its ability to construct a fort but you always need combat troops in the FZ to actually increase the Fort level?
Yes u can do this, I'd say its not very used as it costs AP to attach units and remove them too. Making it rather more expensive overall. Most(not all) tend to move actual units into/adjecent the hexes of FZ and then use the Construction value of those units as digger. FZ will dig a bit in it self but mostly its "used" to get around the max 2 fort level limit.
It'll take a long time and effort to go from FZ to Fort level 5, but once you get to Fort level 3 you don't need to keep the hex garrisoned with combat troops because the Fort won't decay?
On the other hand Level 1 and 2 Forts will decay over time. The presence of a FZ can halt that decay but won't lead to an increase in the Fort level?
U can only get 5 in port hexes, but yes getting fort levels 4 and 5 is hard. The non garrison decay rule is now set at fort level 4 or higher, not 3.
Yes a FZ less at really low ToE will stop decay as its a unit. It can increase fort levels as it has a constuction value. Tho even at 100% ToE its relatively low. Why most ppl tend to move units into the hex build it up to 3-4 then move the units to the next hex to play diggers.
Forts are a seperate entity from FZs, so if a FZ is disbanded, the Fort remains in place and gives its defensive value to any combat unit in that hex? Does this mean that a Fort has no intrinsic combat value - kind of like an ungarrisoned castle - but can only be used by the side who built it? Seems odd?
Well there is no such thing as forts, there are FZ but many call them forts for short and then fort levels. See above.