He's referring to this battle, I had the city of Bielostok under siege for a while with what appeared to be a Russian unit under the Czar trapped inside, I decided it was enough and assaulted the place wiping his whole unit out.
It left me confused as what would cause a drop of 60NM, I thought at first that I've might have killed the Czar in battle. This however came to my mind a turn later so couldn't double-check the messages to see if that where correct as I didn't spot it the first time I scrolled through the messages. So I just opened up my save game as the Russians and checked if he was still listed, first thing I noticed was that he's no longer the GHQ of the Russian Army but after going through the forces list and just filter them by stats and just look for the lowest (he aint hard to spot in that regard

) I've found him locked in Petrograd. Did I injure him? or is there something else going on here?