What distinguishes credible deterrence from mere capability?

While capability refers to possessing the means to inflict damage, credible deterrence goes further by ensuring the adversary believes that the state *willactually use that capability if provoked. Mere capability is simply having the weapons, forces, or resources to respond to an action; credibility is about convincingly communicating the willingness and resolve to do so, making the threat believable. Credibility depends on several factors, including a clear articulation of red lines (the point at which retaliation will occur), a demonstrated history of following through on threats, and a commitment to defending vital interests. It also requires the adversary to perceive that the state's leadership is rational and capable of making difficult decisions, even in the face of high costs. For example, a country might possess a large nuclear arsenal (capability), but if its leaders are perceived as unwilling to risk retaliation, or if its command and control systems are vulnerable, its deterrent may not be credible. Conversely, a country with a smaller but more survivable and reliably controlled nuclear force, coupled with a clear and consistent policy of nuclear deterrence, may have a more credible deterrent. Therefore, while capability is a necessary condition for deterrence, credibility is what transforms a potential threat into an effective deterrent. The adversary must believe that the state has both the *abilityand the *willto respond.