How badly would a decades long war screw over an economy?

Note: Lately, I've wanted to make a Redwall inspired world of woodland animals but can't really decide on Exactly how, I've been looking towards various places for inspiration and playing with various ideas, this is one of the ideas I'm playing around with and may or may not even end up going with. I just want a little feedback on it.

Ok, so imagine a world of sapient woodland animals that has a technology level around and first or second world war. One day war breaks out between multiple factions (I haven't decided how many factions but ideally around than 6 or 7) splitting the land into control of the various political/military factions, each pretty much making their own state while at war with each other. This has been the case for decades (probably like 30/40 years).

How badly would this fuck up the economy? Like, war is very bad for a nation economy. Just a few years of war can royally fuck up an economy for years after, how bad would it be after multiple decades of non-stop war? I came up with this concept a while back but never really did anything with it and I'm thinking of experimenting with it a little.

More Context: If you want more context, I don't have much but this is what I got so far: There are multiple animal factions with different beliefs and stances ranging from ideological, religious, supremacist, economical, etc. The war initially broke out when the ruler of the woodlands died unexpectantly (ending the bloodline of their royal family) resulting in an ever escalating series of events that eventually lead to several different political factions, military groups and even a few religious organisations all fighting for power and control over the Woodlands.

Tl;Dr: the Woodlands are seriously fucked up by decades of Civil War and I want to know how much that would ruin the economy.