Challenges to U.S. Extended Deterrence on the Korean Peninsula and Devising a Strengthened Allied Deterrence Strategy against North Korea

Executive Summary

The Republic of Korea (ROK)-U.S. alliance has endured North Korean challenges for nearly seven decades and deterred North Korean aggression into the South. Amid diplomatic stalemate, North Korea’s nuclear and missile capabilities have increased despite mounting international pressure and economic sanctions against North Korea. The ongoing massive nuclear modernization and the armament of China and Russia’s nuclear forces in the region are challenging U.S. policymakers, and the credibility of the U.S. extended deterrence is now being questioned more by its allies and partners.

Considering the negative repercussions from a ROK pursuit of developing national nuclear weapon capability, this paper is focused instead on exploring ways within the bilateral alliance framework to effectively strengthen the U.S. extended deterrence commitment to ROK against North Korea.  

Derived from traditional deterrence theory and two policy reports, this paper analyzes U.S. extended deterrence on the Korean Peninsula through five significant factors which are deeply associated with U.S. extended deterrence posture: North Korea’s Motivation/Capability, Deterrer’s Capability, Deterrer’s Communication, Deterrer’s Credibility, and Assurance to ROK. 

North Korea’s motivation behind the development of its nuclear and missile capabilities may be limited to intimidation, coercion, and deterrence in use of its nuclear weapons. However, as the number of North Korea’s nuclear arsenal and Intercontinental Ballistic Missiles (plus Submarine Launched Ballistic Missiles) increase significantly enough to credibly threaten the continental United States, North Korea’s nuclear doctrine can be modified to become more aggressive, undercutting the reliability of the U.S. extended deterrence on the Korean Peninsula. 

Deterrer’s Capability includes conventional, nuclear forces and missile defense from both the ROK and United States. The capabilities of both armed forces are robust, and they are maintaining qualitative superiority by further modernization and development. Military capabilities should be buttressed by using other nonmilitary means of economy, information and diplomacy for deterrence.  

Deterrer’s Communication is demonstrated by U.S. high-ranking officials’ statements and strategic documents that reiterate a strong commitment to provide extended deterrence to the ROK.

Deterrer’s Credibility is reinforced by various evidence such as a mutual defense treaty, high-level bilateral security consultative mechanisms, combined exercises, and the presence of the United States Forces Korea (USFK)—and especially both the ROK’s and United States’ increased efforts to strengthen extended deterrence from the bilateral meetings.  

U.S. Assurance to Allies cannot be separated from U.S. extended deterrence. As evidenced by ally’s dilemmas such as De Gaulle’s Doubts, the Leaky Umbrella, Healy’s Theorem, and Defending the Status Quo Ante, the United States needs to address and manage allied concern for the reliability of U.S. extended deterrence.  

Here are some recommendations:

• strengthen the current regularly held ROK-U.S. bilateral security consultative meetings;
• establish a multilateral U.S. extended deterrence consultative group in Asia;
• enhance the credibility of the ROK’s conventional deterrence against North Korea;
• strengthen the level and scope of the ROK-U.S. bilateral combined exercise; and 
• exploit all the nonmilitary means such as diplomacy, economy, and information.

The views presented in this work represent those of the author and do not represent the views of the Republic of Korea government or the Republic of Korea Army. 

Seunghyung Lee was a visiting fellow with the Office of the Korea Chair from 2020-2021.