The 'unstoppable Russian imperial juggernaut' type novel made its appearance during the height of the Tsarist Empire and the Great Game era, then had a revival during the Cold War.
What books do you know of that covers this set of tropes? They don't have to be strictly realistic of course, and can include fantastical or scifi elements. The Russian conquests don't have to be the central focus of the book either, it can appear as background.
by Worried-Boot-1508