I’m reading James McPherson’s “Battle Cry of Freedom” and in the chapter on the wrangling by the South to gain diplomatic recognition by the European powers McPherson mentions the French proposed that France, the UK, and Russia jointly call for a six month armistice but “this so blatantly favored the South that pro-Union Russia quickly rejected it.” The book doesn’t say why Russia was pro-Union in its outlook and I’m curious if anyone knows what the Russian calculations were at that time.
I touch a bit on this in this older answer, discussing how Russia saw the US as a counterweight of international support in her arguments with France and England.