Vali Nasr writes: Over the past two months, even as American-trained forces were driving Islamic State insurgents out of the major Iraqi city of Mosul, the war next door in Syria was taking a dangerous but little-remarked turn — one far more favorable for Russia’s ambitions to regain a position of broad influence in the Middle East.

First, a major gaffe by President Trump helped Saudi Arabia split a Sunni Muslim alliance that was supposed to fight against the Islamic State — so much so that Qatar and Turkey moved closer together and became open to cooperation with Iran and Russia. Later, when Mr. Trump sat down with President Vladimir Putin of Russia in Germany, the American president virtually handed the keys to the region to his adversary by agreeing to a cease-fire in Syria that assumed a lasting presence of Russian influence in that conflict — which only consolidated the likelihood of wider regional influence.

With Mr. Trump’s inner circle often at odds with one another and the president going his own unpredictable way, Mr. Putin seems never to miss an opportunity to expand Russia’s presence in the region. That has helped to blur even the longstanding lines of sectarian division between Sunni and Shiite states and to complicate America’s strategic position.

To be sure, Mr. Trump sent his secretary of state, Rex Tillerson, to the region to sort out the mess. But among the monarchs of the Middle East, an underling’s voice stood no chance of undoing the damage already done by his master’s tweets. [Continue reading…]