In deciding to target bond yields, Japan is deploying a monetary strategy to combat deflation used by its former enemy in World War II. The trouble is that America's experience back then suggests the tactics probably will not work on their own.

Economists who have studied that period say it was increased government spending, along with heightened inflation expectations, that eventually led to a stepped-up pace of U.S. price increases more than a half century ago.

Once inflation was humming along, the Federal Reserve's strategy of pegging long-term interest rates did nothing to put a lid on it, which is why the central bank pushed for a 1951 agreement with the Treasury to abandon the long-term yield fix.