How a swap line for Persian Gulf allies would break with the past

If the United States gets into the business of providing dollar liquidity to the United Arab Emirates and other Persian Gulf states battered by the Strait of Hormuz's closure, it will amount to a novel use of an old power.The big picture: The Federal Reserve used swap lines with foreign central banks as a key tool to calm global financial disruptions in periods of stress, starting in the early days of the global financial crisis in 2007. They were driven by Fed leaders' belief that dollar fundin...