Maybe not Alatyr, but Nizhnv-Novgorod, as that's where Alatyr's fort is.
What matters is that OP's scenario really makes zero sense.
Why N-Novgorod? It is his fort. IMO it would be completely inane if the movement depended not only on enemy forts, but also his forts.
Some simple and sensible proposals were presented before, but as Wiz is so fond of "wrong answers" as long as they are his, we wont see much better rules anytime soon.
Simple solution
1) mine fort - I can go always (which is actually subset of 2)
2) province controlled by me, I can go in
3) enemy controlled province, I can go in if movement is not blocked by fort or it is fort itself, otherwise I have to capture fort first - so I can enter enemy ZOC, possibly from many sides, and if I capture provinces I can move between them.
We could add stipulations or variations that e.g. in order to move from one controlled to another controlled enemy province fort must be (actively?) besieged, or add restrictions for movement when enemy captures our fort, or whatever.
But it can be clearly seen, also in bug forum, that requirement that army can go ONLY back is stupid one.
Btw. IMO assumption that garrison can do anything against enemy army, especially if province is hundred km wide, is ahistorical, but game must have some rules. Whatever threat to supply lines we imagine it was not infantry (or city militia) from garrison, but cavalry and desperate peasantry.