President Donald Trump made a sweeping decision in August 2017 that could have rocked the global economy: the U.S. would pull out of Nafta, the World Trade Organization, and its trade deal with South Korea. Alarmed, Trump’s top staffers scrambled to stop him, according to Bob Woodward’s new book, “Fear.” Bloomberg News obtained a copy of the book ahead of its release, which is scheduled for Tuesday. Then-top economic adviser Gary Cohn and staff secretary Rob Porter pulled chief of staff John Kelly into the Oval Office to convince Trump to back down.