They’ve expelled diplomats. Imposed sanctions. Fought proxy wars. Their war of words never really ends. But despite the often thorny relationship between the U.S. and Russia — and notwithstanding the brief “recall” of ambassadors that ended with a Biden-Putin summit last week — the last American ambassador to Moscow to be declared “persona non grata” and expelled by Russia was George F. Kennan in 1952. 

It was the Soviet Union back then, and Joseph Stalin was in charge. 

And yet that isn’t the reason Kennan is still remembered in the corridors of power in Washington — and Moscow. Kennan’s most consequential contribution