Alliance Structures, Collective Identity and Regional Difference in the Credibility of U.S. Extended Deterrence

Deterrence can be divided into "direct deterrence" that deters opponents from launching attacks on the homeland and "extended deterrence" that deters opponents from attacking third countries in terms of the protected objects. The "extended deterrence" involves issues of capability and credibility. The United States provides "extended deterrence" protection to its allies in the form of a "nuclear umbrella". However, there is a significant difference in the credibility of the extended deterrence provided by the United States among its allies in the Asia-Pacific region and Europe. The questions this paper attempts to answer are: Why does the credibility of the U.S. extended deterrence differ between its Asia-Pacific and European allies? Why does the United States promote "nuclear sharing" arrangements in Europe while implementing "nuclear monopoly" in the Asia-Pacific region to suppress the demand for developing nuclear weapons? This paper holds that "alliance structure" and "collective identity" have a strong positive correlation with extended deterrence, and at the same time, the effect of "collective identity" is stronger than that of "alliance structure". Both can affect the "credibility of extended deterrence" by changing the "bargaining power".