Among the most cited risks are: nuclear proliferation contributes to the risk of unstable governments or leaders gaining access to nuclear weapons and using them in an irresponsible way; in countries newly acquiring nuclear weapons, safeguard systems preventing nuclear accidents and incidents may be insufficient or altogether non-existent; in regions dominated by a high degree of tension, a nuclear power may be tempted to launch a pre-emptive nuclear strike before its opponent has also gained access to nuclear weapons. The initial phase of regional nuclear arms races are is prone to strategic instability. A local nuclear war may involve major nuclear powers through multilateral defence treaties or perceived threats. An unidentified nuclear strike against a nuclear power may be misinterpreted and lead to a punitive strike against the wrong opponent. Smaller nuclear powers may be manipulated into making nuclear attacks. Private corporations and groups outside governmental control, including terrorists and criminals, may acquire access to nuclear weapons.
The possession of nuclear weapons has led governments to behave with increased political and military caution and circumspection. There are no convincing reasons to assume that in case of a local nuclear war the major nuclear powers and their defence alliances would fail to react with great care and try to limit the nuclear exchange unless they had made irrevocable nuclear commitments for mutual defence. There is no internal logic or compelling necessity for a bilateral or even regional nuclear conflict to develop into global nuclear war. The possession of nuclear weapons by groups outside governmental control would be aimed at blackmailing rather than at actually using the arms. If they are used, this would amount to national tragedies in the countries in which they would occur, but would not necessarily entail escalation into global nuclear war.