What would cause Persia to do this? Afaik she had suffered at Russian hands just as much as Turkey.
Weren't Persia and the Ottomans historically hostile to each other, though?
Also, I suppose that the Persian Shah might want to put as many Shiites as possible during his rule; indeed, that could be a good motivation for a Persian declaration of war on the Ottomans. Basically, think of a Shiite version of, say, German unification or Italian unification.
As for her battlefield performance, probably nothing special. The Turks gave a good account of themselves even against the Russians, and Persia ain't in the same league.
Couldn't fighting against both Russia and Persia strain Ottoman resources?
If lucky she might get a village or two in Armenia for her trouble.
What about in the Middle East? Specifically, which parts of Iraq--if any--would Persia acquire after the war in this TL?
I think this could make a League of Three Emperors more feasible in the long term.
Why exactly do you say that?
She gains the Basra Vilayet and suzerainty over al-Hasa east coast Arabia?
Sounds reasonable--as least with a sufficiently good victory of the Russo-Persians in this war.
However, Persian control over al-Hasa could trigger a future war between Persia and the House of Saud.
I don't think Persia could *earn* the land with her own military, but if making an effort and favored in the settlement, it could happen.
So basically, Russia would use her own military successes on the battlefield as bargaining chips to get Persia something in the post-war peace settlement?
However, I don't know if both Russia and Britain would be agreeable to Persian expansion at the same time.
Why exactly wouldn't they be?
Persia wins some hinterland, but that's about it. Russia has little to gain by bringing Persia into the conflict.
Hinterland where exactly?
If Persia is really that bad militarly, could we see thrm actually crumble?
Frankly, I suspect that Russia will directly militarily prop up Persia if push comes to shove and the worst happens.