WASHINGTON—President Trump’s decision to double steel tariffs on Turkey as its government battled a currency collapse marked a departure for the U.S. from how it traditionally handles financial turmoil hitting emerging markets.
Washington has generally tried to calm global markets in such moments, especially when investors are gripped by fear of contagion. Mr. Trump instead squeezed Ankara further, raising tariffs on Turkish steel imports to 50% and aluminum to 20%, which deepened the Turkish lira’s drop and worsened market...