(Super-spoilers ahead, kind of.)
As the breaking of the world begins, civilization - and the Aes Sedai especially - have a very good grip on what's going on. They might not be aware of the identities of all darkfriends, but they know many/most of the Forsaken and the dreadlords, certainly the the ones who declared for the Dark One or were banished for dark-friendly activity; they probably know about Ishar Morrad Chuain's breeding of the Shadowspawn (and certainly know about the experimentation and breeding program generally, since it involves tens of millions of people); and of course they know all of their own strengths - weaves of the power, talents, power-assisted technology, catalogue of angreal, terangreal and sa-angreal; metaphysics of the bore (as far as they've studied it anyway); etc. etc.
Somehow, they lose all of this information. Now, one could "blame it on the darkfriends" for expunging some records from the Aes Sedai records (at the Hall of Servants, and later, the White Tower library). But even assuming they were able to do that much damage, over time, to the records at White Tower - that still doesn't explain much. Everyone who's ever kept records in an organization or has managed in a library knows that management of copies and replication vis-a-vis other libraries is important. And of course, they had printing presses at the time of the breaking, and schools and universities, and there were other libraries around the continent and the world.
Now, if the Aes Sedai, and the human communities surviving the breaking, had bothered to keep records and make copies of them (rather than a sensitive single-record-set, when they know they're riddled by enemy agents) - would they not have had a pretty easy time keeping the Shadow at bay? Or doing even better than that?
I was motivated to ask this by the scene in the TV series, S01E08, where Althor and Damodred are being a bunch of happy-go-lucky idiots who have no idea about anything, and would well deserve just being killed off on the spot by somebody far weaker than Tedronai. I realize the show's story is not the same as the books, but still.