While our knowledge of the moments just before the Great War is highly limited, it is a safe assumption that the Chinese spies were stationed in D.C. to provide adequate bombing targets and information on enemy defenses before the nukes were inevitably dropped. While many people would have you believe the Great War was sudden, the truth is that there was some sort of nuclear warfare expected for months before it finally happened, although not on the scale that lead to the creation of the Capital Wasteland and the current state of the world in general. Chinese goverment would have surely been prepared for the eventuality of starting or responding to a nuclear bombing.