Since the Soviet Union dissolved several decades ago, one of the most prominent foreign-policy aims of powerful countries has been to constrict the spreading of nuclear weapons worldwide. When such leading powers possess the nuclear power, or when they are even allied with nuclear-possessing states, they have the power to pressure other perceived weaker/non-nuclear states from developing and obtaining nuclear weapons themselves. No country in the world has a global nuclear monopoly; however, nuclear-armed countries wish to preserve their clout over non-nuclear countries, as there are fewer risks associated with attacking non-nuclear countries in comparison to attacking nuclear armed countries.
Additionally, countries desire nuclear weapons because it makes them a leading force in developing or future wars. They can pressure, coerce, or threaten other states and countries into complying with new policies or other restrictions. When a state obtains nuclear weapons, the cost of invading that state elevates drastically, which makes it exceptionally more difficult for the invader to acquire any military power over the other. In this way, the desire for nuclear weapons is not just to have power, but also to restrict others from acquiring such power. More often than not, nuclear-armed states place heavy emphasis on preventing the spread of nuclear arms, simply to preserve their own power and authority over everyone else.
Possessing nuclear weapons has, throughout history, shown it can instill fear and anxiety in countries on the other side of the world. For example, in World War II, the threat of nuclear warfare was constant, motivating families across America to build bomb shelters. In this way, nuclear weapons are both physically and mentally powerful in shaking other countries or states. Thus, nuclear weapons are desirable for many countries, but primarily because they give countries and states a military edge.