What is the primary purpose of a nuclear weapon?

The primary purpose of a nuclear weapon is to serve as a deterrent against aggression. This means that the existence of nuclear weapons is intended to discourage countries from engaging in hostile actions or initiating conflicts with one another. The rationale is that the devastating consequences of nuclear warfare create a significant risk that any aggressor will reconsider their actions, leading to a stability of power among nations.

This deterrent effect hinges on the idea that the potential retaliatory response to a nuclear attack is so severe that it effectively prevents such attacks from occurring. Countries with nuclear weapons often maintain a policy of "mutually assured destruction," which reinforces this deterrent theory.

In contrast, other options suggest uses for nuclear weapons that do not align with their intended strategic role in international relations. While promoting peace or assisting in civil defense may be desirable goals, they do not capture the primary purpose behind the development and stockpiling of nuclear arsenals by nations.