The thesis is devoted to the study of impact of nuclear factor on regional systems of international security. The thesis includes both conceptual-theoretic and applied author's researches. It was proved that the impact of nuclear factor on regional security was not unambiguous and depended on type of dyads and of nuclear doctrines. The key factors, which swayed a state to the adoption of the decision about the launch of nuclear weapons construction program or restrain from such decision were detected. After the Cold War confrontation in the nuclear sphere moved to the regional level, for which the logic of confrontation between nuclear superpowers is irrelevant. There are two basic approaches to the influence of the nuclear factor on regional security: 1) nuclear pessimists believe that increasing number of nuclear states will increase the chances of irrational behavior and trigger a nuclear war; 2) nuclear optimists consider that the spread of nuclear weapons will help to reduce the number of conflicts due to the deterrence. In his turn, the author is proponent of an alternative view that the impact of the nuclear factor is different and depends on the kind of dyad and type of nuclear doctrine. In the thesis the three regions - East Asia, South Asia and the Middle East, in which nuclear factor plays a crucial role for regional security, are analyzed. In East Asia the formation of regional nuclear leader - China, which has the ambition to join the club of the nuclear superpowers, is in progress. But for this Beijing must prove its ability to keep the situation in the region under total control - to impose its vision of the North Korean crisis resolution, solve local territorial disputes, and prevent the spread of nuclear weapons to non-nuclear countries in the region - Japan, South Korea, Taiwan. South Asia is the only region where regional system of nuclear deterrence is forming. Such a system differs from the Soviet-American relations due to a small distance between the opponents, and the imperfection of the technical means of detection and alert. Nevertheless, the deterrence system has already proved its effectiveness in preventing large-scale conventional conflicts, however, does not exclude the low intensity conflicts. The main threat to stability in the region is the ability of terrorist organizations to capture the components of nuclear weapons or loss of control over nuclear weapons as a result of destabilization of the political situation in Pakistan. However, the situation is also under the constant supervision of external regional players - the United States and China, in which interests is to preserve stability in the region. Today in the Middle East one de-facto nuclear state (Israel) and a threshold country (Iran) are situated. The main challenge to the security of the region is Iranian nuclear program, because in the case of its successful completion there could begin "nuclear domino" in the region among Arab countries that claim to regional leadership. Moreover, Israel, for many years successfully pursuing a policy of "nuclear opacity" will be forced to officially recognize the existence of Israeli nuclear weapons, to lower the threshold of its application, and may even try to make a preemptive attack on Iranian nuclear facilities. The most affordable option for complex resolution of nuclear problems in the Middle East would be to create a nuclear-free zone, however, this requires a political consensus of all States in the region.
