It must be obvious even to him, by now, that he has no hope of winning anything of value to Russia in this war. Victory means diverting scarce resources to hold down an inevitable guerilla insurgency, and setting off a scaled-down version of the Cold War that could last decades -- and victory is not likely to be within his grasp any time soon. He has the power to declare himself satisfied with Crimea and Donbas, and break off the fighting. The Ukrainians certainly would not continue it unilaterally.