Page 206 - Trilateral Korea Japan U.S. Cooperation

alliance but through coordination with other partner countries
as well. The aim is to instill in opposing countries the recognition
that achieving strategic goals through military action is impossible.
Under these circumstances, firstly, enhancing the effectiveness
and validity of mutual cooperation, especially between Japan and
South Korea, and secondly, maintaining the credibility of the U.S.
extended nuclear deterrence, are necessary.

Since the Russian invasion of Ukraine, the credibility of
extended nuclear deterrence has suddenly come under scrutiny
in Japan and South Korea.

North Korea’s aim is to reduce confidence in the U.S.
commitment to extended nuclear deterrence through a
combination of North Korean retaliatory strikes against the
United States and preemptive strikes against South Korea,
thereby dividing the United States and South Korea. In
October 2022, Chung Jin-Suk, a politician of the ruling
People Power Party, raised the question, “If Kim Jong-Un
were to use tactical nuclear weapons on the Korean Peninsula,
would the United States really respond to North Korea with
nuclear weapons in preparation for a nuclear attack on Guam
and Okinawa?” He also said that they needed to take a lesson
from Ukraine, which was exposed to a nuclear threat from
Russia after abandoning its nuclear capability.

Similarly, in a Taiwan contingency, China can gain the upper
hand in the war if it divides Japan and the United States and
prevents Japan from committing to support U.S. efforts to
help defend Taiwan.

206 Section III : South Korea-Japan-U.S. Cooperation: How to Deter Pyongyang and Dissuade Beijing