Forbes:
The U.S. Navy plays a vital role in deterring nuclear aggression with its fleet of ballistic missile submarines. Because the subs can’t be targeted when submerged, they are the most survivable component of the nation’s strategic deterrent. Being able to survive an attack and then retaliate appropriately is what makes a deterrent credible to enemies.
As overseas missile threats spread and diversify though, another part of the Navy is becoming increasingly important to deterring the use of nuclear weapons — or dealing with the consequences when deterrence fails. That is the sea-based air and missile defense system known as Aegis.
The Navy traditionally hasn’t thought about its Aegis destroyers and cruisers as strategic weapons, but they contribute to nuclear deterrence in many ways, from detection and tracking of threats to interception of incoming missiles to cueing of other defensive systems. All of these features can potentially dissuade an aggressor from launching because they raise doubts about the ability of enemy weapons to hit intended targets.
