On a completely unrelated subject, I had a brainwave last night that made me realize that the Collapse was substantially worse than I originally thought.
Consider this: Two years ago, Leaf had around fifty jōnin ninja, mostly spread out in the upper-eschlons of the clans. Then, Leaf lost Hiruzen Sarutobi and most of its high-level ANBU in one night. Not long after that, it lost most (or at least a good chunk) of its remaining jōnin, including many clan heads, at the Battle of the Gods. Then, the Collapse happens and decimates most clans. Compounds were destroyed and many clan elders and high-level clan ninja were killed.
Now, Leaf has only 21 jōnin, some of whom just took the role and some of whom which aren't affliated with the main clans (Naruto, Tsunade, Orochimaru, etc.). In other words, there is a good chance that a lot of clans might not have a single senior jōnin.
Guys, Leaf might have permanently lost most of the jōnin-level techniques of its strongest clans. Hyūga Motokazu is a jōnin, so there's a good chance that he knows and can pass on the upper-level techniques of the Byakugan. The Hyūga are safe, thank god, but what about the Nara and the Yamanaka? HDK whether either one of has a jōnin. In fact, we have explicit confirmation that the Yamanaka have lost ninjutsu techniques from Ino.
Upper-level clan techniques and secrets don't get told to members until they reach a certain level. For jōnin-level techniques, that level may very well be "jōnin" or "experienced clan elder," the population of which may have dropped to zero for some clans after the Collapse. For the very best techniques, it might even be "senior jōnin." It's not totally hopeless because jōnin are rare and most clans probably didn't have more than two or maybe three at a given time, so many clans probably had contingencies for suddenly losing a few high ranking members. Unfortuntately, the Collapse didn't just kill the jōnin; it also killed the clan elders and destroyed entire clan compounds (where most records would be stored). It also happened right after many clans had already lost many of the people who would be expected to help rebuild. There's a good chance that this scenario goes well beyond what most clans expected as a worst-case scenario.
This is a devestating and permanent blow to strength of both our allies and Leaf itself.
[Part 1/3]