The conventional military superiority no more guarantees the security of the United States. The emergence of the "grey zone" transformed the security paradigm for the US. The two main adversaries of the US in the grey zone, China, and Russia, have learned that if they cannot compete with the United States conventionally, they can undermine the US security in cyber, economic, and information domains through offensive activities in the grey zone.
Thus, they integrated grey-zone operations into their strategies: while China hopes to make the world safer for its authoritarianism, Russia aims to weaken NATO and command its former Soviet "near abroad". The "grey zone" refers to the hybrid threats that combine information operations, political coercion, economic coercion, cyber operations, proxy support, and provocation by state-controlled forces.
Grey zone attacks can hit closer to home, and exploit societal cleavages and domestic vulnerabilities. In this environment, the traditional American conventional deterrence model does not work, and it requires the United States to adapt its foreign policy and military institutions to a post-Cold War world. If the US continues to view homeland defence and global interests separately, it leaves a blind spot for competitors to exploit.