The Korean Conflict has been among the most powerful pillars of the balance of power in Northeast Asia. Yet, that balance changed after North Korea launched its nuclear program. The American presence in the region, on the other side, has had considerable implications for South Korea's national security and its capabilities to defend. The purpose of this chapter is two-fold. First, it theorizes the security dilemma between North and South Korea and calculates the probability of nuclear escalation. Second, the chapter explores the effects of North Korea's nuclear program on the bilateral relations between Washington and Seoul, particularly regarding Pyongyang's consistent rapprochement with Russia. The most important point of this study is to challenge the statement that South Korea can effectively deter the North without achieving nuclear parity with Pyongyang. Finally, the chapter stresses the difference between the Korean Peninsula's old and new realities.