On Feb. 15, just as Chinese Vice President Xi Jinping arrived in the United States for a four-day visit, U.S. President Barack Obama told an audience of American workers in Milwaukee: "Manufacturing is coming back!" Coming back from China, that is. But while the Master Lock Co. of Milwaukee has moved some jobs back to the United States, everybody knows that the flow will really continue to be in the other direction.

It doesn't matter whether China's economy finally overtakes America's in 2020, or 2025, or 2030. A great shift of productivity and wealth is under way, and economic power generally translates pretty directly into military power. So will the United States and China be able to manage the shift without a great war?

At the end of Vice President Xi's U.S. visit on 18 February, the future Chinese leader assured delegates at a trade conference in Los Angeles: "A prosperous and stable China will not be a threat to any country. It will only be a positive force for world peace and development." Perhaps, but everybody else is very nervous about it.