Why *didn't* Dumbledore fill DADA post? (Re: Potion Master...)

[laura]

No: HPFGUIDX 83523

Iggy here:
> You could also have the fact that AD really knows a lot about 
> the nature of the Trio, and allowed Umbridge into the DADA 
> position because he had a hunch that the Trio would create 
> something like the DA, like they did...


laura here...
I certainly think that Dumbledore would know that the trio would 
attempt something like the DA, and reading OOTP last night I found 
something I thought was interesting, a little odd...in the room of 
requirement was 'a large, cracked foe-glass that Harry was sure had 
hung, the previous year, in the fake Moody's office' (uk edition p346)
Why would't it have been a nice shiny unbroken foe-glass? And why the 
connection with fake Moody? I'm pretty sure this is relevant somehow, 
and I'm inclined to think that Dumbledore is behind it, but why that 
particular object completely escapes me...any ideas people?

laura