Realm Divide triggers

There's been enough discussion about the event in the Tea House to make me think it deserves its own topic in this forum. Mainly, I want to figure out exactly what gets the game to decide that it's time to throw everything it has at you. As I myself have only encountered the event once so far, I won't be of that much help providing anecdotal evidence, so this initial post will be more of a "general factors/questions" thread.

What we know: Realm Divide is caused by your clan's reputation bar to be full. This event happens immediately after that condition is met, with the actual war-declaring to take place the following turn.

What we're not sure of: What exactly gets the bar to move all the way up? Does the province limit differ depending on chosen faction, game difficulty, and campaign length? Is there anything tied to it aside from the capture of cities (for example: Daimyo stats or a lot of notable victories)?

Anecdotal:

In a previous H/H/L game RD triggered with my 19th province (I was able to get 18 without triggering it.) No vassals.

In my current VH/VH/L game RD is going to trigger with my 18th province (I am only able to get 17 without triggering it.) No vassals. I can also see the bar move with some heroic victories which I could not in my previous game.

The impact of victories wasn't too appreciable in my previous game and I was wondering if they really filled the bar. For myself, I'm convinced that they do. In fairness, I've been in war far more in my VH game, but given that I can visibly see the bar move, it's also possible that the bar is effectively shorter as difficulty increases (even if it isn't visibly shorter).

Added a couple screenshots from my VH/VH/L game. It's easiest to see this at the end of the bar as there are no points of reference until you get to the end.

Starting fame:

https://img696.imageshack.us/img696/421/prefame.jpg

This is the same turn. Same number of provinces. The only thing I've done is win two heroic victories:

https://img858.imageshack.us/img858/239/famer.jpg

I could win heroic victories towards the end of the fame bar on my H/H/L campaign without seeing the bar move this clearly. This is why I wonder if it fills faster as difficulty increases. But it's also possible that I've just fought a lot more in this campaign and somehow didn't notice it move this clearly on H/H/L.