Trump shouldn’t repeat Obama’s mistake in Iraq and Syria Members of the U.S.-backed Syrian forces that captured Raqqa take a selfie Oct. 20 at the stadium where Islamic State fighters made their last stand in the city. (Asmaa Waguih/AP) THE FINAL capture of the Islamic State’s de facto capital of Raqqa  this week by U.S.-backed Syrian forces brings the would-be caliphate to the brink of extinction: It has  lost 87 percent  of the territory it once controlled in Iraq and Syria and probably will soon be driven from the rest. But the terrorists’ defeat raises complex challenges for the United States in Iraq and Syria, where Iran and Russia are  entrenching their forces  and consolidating influence at the expense of U.S. allies. If there is a countering American strategy, it isn’t evident. While gratuitously  undermining  the Iran nuclear agreement, President Trump promised that the United States would resist Iranian aggression in the region. Yet the...