“Who rules East Europe commands the Heartland;who rules the Heartland commands the World-Island;who rules the World-Island controls the world.”(Halford Mackinder. “The Geographic Pivot of History”))
Russia + China = a pretty big pivot in the center of the world-island.
But for the next big conflict, throw in the two powerful blue water navies of the heartland powers, Russia and China
Of course the Clinton-Rodham-Kerry strategic geniuses in the US State Department are sure Russia and China will never ally because they are rivals, that’s what their Ivy league armchair geopolitical strategists taught them.
That, and being accommodating to Iran will encourage the emergence of a “moderate” regime (been hearing that one from liberals since 1979.
I see that deal as a matter of mutual economic survival, not conquest.