Missing Turk units

[Deus ret.]

these units can only be built in the province that contains the Military Academy? So even if I teched up to the right level in other provinces they will be un-available there?

Correct. That's a sad thing since there is more than one province giving a bonus to Janissary units IIRC (BTW are the Turks able to recruit Hashishin? I don't think so, but if they are, they also would have to be built in the same province because of the required Grand Mosque).
The exploit described by Geezer57 provides a remedy, but consumes quite a lot of time, so you should make sure to start in High to have enough breathing space for the buildup. Janissaries already become available in High anyway, even if they shouldn't.

[caravel]

Georgia is famous for it's Janissary Archers and Bulgaria for it's Janissary Heavy Infantry. It's pretty obvious which province you should build your grand mosque in if you're heavily into Janissaries. Janissary Archers aren't much use, so there's really only one choice.

If like me, and you only train limited Janissaries, then you may want to build your Grand Mosque in another province to boost the morale of the troops trained there at a bonus, troops that unlike Janissaries could do with a morale boost. This is why I usually build my grand mosque in either Rum, Tripoli or Lesser Armenia.

[Third spearman from the left]

Deus ret.

yes the Hashishin can be built by the turks. and they can be built outside the province that contains the grand mosque as along as they have ribat and a master swordsmith.

thanks everyone for the info, first time ever playing the turks, even though I've been playing MTW for ages.

[Deus ret.]

Deus ret.

yes the Hashishin can be built by the turks. and they can be built outside the province that contains the grand mosque as along as they have ribat and a master swordsmith.

I confused them with Nizaris, sorry!