The picture says it all: Marco Rubio and Sergey Lavrov, America and Russia, sat about a hardwood table beneath the dripping chandeliers of Saudi Arabia’s Diriyah Palace, ready to remake Eurasia for the rest of the century. Between them sits Prince Farhan bin Abdallah, the Saudi foreign minister, and cousin to Crown Prince Mohamed bin Salman (MBS). Delegates from Europe and Ukraine are nowhere to be seen. The message from Donald Trump’s peace talks on Tuesday is clear: Saudi Arabia is now the...