Here's the situation: I'm playing the Ottomans in 1852, and Russia declares war on me. Britain and France declare war on Russia (the Crimean War). Several huge Russian armies bear down through the Caucasans and the Balkans towards Constantinople, eventually depressing Ottoman morale below 70. The French make an incursion west of Odessa, then disappear. A brigade of French appear near Symrna, then do nothing. Where's Lord Cardigan? Indeed, where are Raglan, Lucan, Scarlett, the lot of the red coated host? Nowhere to be seen. I always knew AI allies aren't worth spit. I have to wait for the Czar to offer a ruinous peace.
My question is: if I want to take over a allied country during the course of a war to use their armies and navies and prevent the above from happening, and then return them to AI control at a later time, is this possible?