I guess I misused the phrase back channel; I didnt meant POTUS and Putin were communicating indirectly. Trump likes regular phones. Putin doesnt speak English, IIRC. Didnt Melania act as translator for them before? Putin must know another language that Melania knows.
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Yes, German. Putin was stationed for a long time in East Germany and is fluent in that language. He also understands the West better than many of the Russian leaders I think, because of that.
I was thinking German most likely. Melania speaks, IIRC, five languages! What a brain.