Scott Douglas Sagan is the Caroline S.G. Munro professor of Political Science at Stanford University and co-director of Stanford's Center for International Security and Cooperation (CISAC). He also is one of the leading pessimist scholars about nuclear proliferation, and his co-authored book with Kenneth Waltz, "The Spread of Nuclear Weapons: A Debate Renewed", is widely read and cited in the literature on nuclear weapons.
Sagan a nuclear pessimist discussed in this article why states go nuclear? , most of the literature and realists believe that it is due to security states go nuclear, but Sagan challenged this simplistic view and explained it considering three models namely: “the security model,” “the domestic politics model,” and “the norms model.”
In security model states go nuclear due to the foreign threats especially nuclear threats. Stronger states mostly go for their own nuclear programmes while the weaker states form alliances with the stronger nuclear states. States like United Kingdom and France built their nuclear weapons due to growing soviet threat and due to decrease in the credibility of US extended deterrence. China built its nuclear weapons because it was threatened by US during Korean War and Taiwan straits crises, India built its nuclear programme due to security threats from china after china tested its nukes in 1964 just after the Sino India war in 1962.
Contrary to nuclear Proliferation State like South Africa destroyed its nuclear weapons in 1991 due to reduction in its security threats. This shows that states may give up their nuclear weapons if their security threats are eliminated.
In domestic politics model nuclear weapons are used to gain limited political and