Tsar Nicholas II had taken the consequences of the Russian Civil War to heart. Forced to draft a constitution rather quickly following the defeat of the Bolsheviks in order to appease the aggrieved people of Russia, he had largely based it upon the German Constitution.
Meaning that the Tsar only had the power to declare a defensive war. As for any offensive war that was up for the State Duma to vote upon. Even so, he retained significant authority over the military, meaning that he had the power to simply not mobilize his forces even if the State Duma declared war on Germany in the coming years.
But that was starting to seem less and less like a possibility. Bruno's actions in Russia had changed things quite significantly. The man was viewed as a war hero by the nation, and the humanitarian efforts undertaken by the Iron Division, and the means of support they left behind after withdrawing, had left a good reputation of Germany on the Russian people.