In 1971, President Nixon imposed national price controls and took the United States off the gold standard, an extreme measure intended to end an ongoing currency war that had destroyed faith in the U.S. dollar. Today we are engaged in a new currency war, and this time the consequences will be far worse than those that confronted Nixon.

Currency wars are one of the most destructive and feared outcomes in international economics. At best, they offer the sorry spectacle of countries' stealing growth from their trading partners. At worst, they degenerate into sequential bouts of inflation, recession, retaliation, and sometimes actual violence. Left unchecked, the next currency war could lead to a crisis worse than the panic of 2008.

Currency wars have happened before-twice in the last century alone-and they always end badly. Time and again, paper currencies have collapsed, assets have been frozen, gold has been confiscated, and capital controls have been imposed. And the next crash is ov