U.S.-Turkish relations are mired in the worst crisis of their history. Turkish President Recep Tayyip Erdogan is demanding that President Trump turn over Mr. Erdogan’s sworn enemy, Fethullah Gülen. Mr. Trump, meanwhile, seeks the release of the American pastor Andrew Brunson, who was imprisoned on the pretext that he had been involved in Turkey’s July 2016 coup attempt. The U.S. government has levied economic sanctions on two senior Turkish officials, akin to those imposed on Russian oligarchs after the seizure of Crimea. Turkey responded by freezing the plainly nonexistent Turkish assets of two Trump cabinet members....