South Korea and the United States signed joint guidelines Thursday to ensure a swift and decisive response to any North Korean nuclear attack by integrating South Korea's advanced conventional forces and US nuclear capabilities into a strengthened combined defense strategy.

The "Guidelines for Nuclear Deterrence and Nuclear Operations on the Korean Peninsula" were signed by South Korea's Defense Ministry and the US Defense Department just before the summit between South Korean President Yoon Suk Yeol and US President Joe Biden in Washington.

"The Presidents underscored that the guidelines document provides a solid foundation for enhancing US-ROK extended deterrence cooperation in an integrated manner," the joint statement of the two leaders read, referring to South Korea by its acronym of the country's official name, the Republic of Korea.

“The guidelines document provides guidance to Alliance policy and military authorities in maintaining and strengthening a credible and effective nuclear deterrence policy and posture,” the statement continued.

The guidelines document, released as a key outcome of the “Nuclear Consultative Group," followed the group's inaugural meeting in Seoul last July.

The NCG is designed to enable the allies to jointly conduct nuclear planning and outline scenarios for using the US nuclear arsenal in the event of a North Korean nuclear attack. The NCG was established as a result of the Washington Declaration, signed by Yoon and Biden on April 26 of last year.

The joint statement on Thursday also read, “The Presidents reaffirmed their commitments in the U.S.-ROK Washington Declaration and highlighted that any nuclear attack by the DPRK against the ROK will be met with a swift, overwhelming and decisive response.”

Significance of joint guidelines

South Korea's Principal Deputy National Security Adviser Kim Tae-hyo said Thursday that the joint guidelines signify the "establishment of an integrated extended deterrence system jointly operated by South Korea and the US."

During a press briefing, Kim further explained that the integrated system means "conventional-nuclear integration" or CNI.

"When we say 'South Korea and the US work together,' it means that the previous extended deterrence was solely decided and provided by the US. Now, it has evolved into a system where our organization, personnel and assets are involved alongside the US in nuclear operations on the Korean Peninsula," Kim said.

"That is, the integration of US nuclear forces with our advanced conventional forces is designed to deter and respond to North Korea's nuclear threats," Kim added.

Extended deterrence is the US’ commitment to deter or respond to coercion and external attacks on US allies and partners with the full range of its military capabilities, including nuclear weapons.

South Korea will therefore now participate in discussions and the planning of US nuclear operations on the Korean Peninsula, compared to the past when South Korea had no voice in mobilizing US nuclear assets.

Kim further explained that, through the integration of nuclear and conventional forces, the South Korean military, alongside US forces, will engage in information sharing, consultations, planning, exercises, training and operations related to nuclear operations on the Korean Peninsula.

The joint operation will enhance the allies' realistic nuclear response capabilities and readiness, according to Kim.

Nuclear-based alliance

Kim underscored, "By completing the 'integrated extended deterrence system between South Korea and the US' through the formulation of joint guidelines, the South Korea-US alliance, which has been based on conventional forces, has been elevated to a fully-fledged nuclear-based alliance."

"The South Korea-US alliance has become a pioneering example of conducting bilateral, direct discussions on nuclear operations through the integration of both nuclear and conventional forces," Kim added.

The South Korea-US joint guidelines have not been disclosed.

However, Kim said the US "has committed to assigning missions to its nuclear assets specifically for the Korean Peninsula, both in peacetime and wartime, to deter and respond to North Korean nuclear threats" for integration of conventional and nuclear forces in the joint guidelines.

"The United States has always declared that it would provide all categories of capabilities, including nuclear, to the Republic of Korea," Kim explained. "However, this is the first time it has been documented that US nuclear assets will be assigned specific missions for deterring and responding to North Korean nuclear threats."

Kim also announced that South Korea and Washington have "established nuclear consultative procedures at all levels of governments, including direct communication between the leaders of South Korea and the US in case of a nuclear crisis."

To support this, both sides have also set up a “communication system for nuclear consultations that enables immediate communication and maintains security,” according to Kim.

Kim explained that Seoul and Washington will also “expand the sharing of sensitive nuclear information” and have adopted security procedures and systems to support this effort.

When assessing the new development Friday, South Korea's Defense Ministry said, "While the existing US extended deterrence commitments that were primarily declarative and focused on deterring North Korean nuclear threats, the new joint guidelines officially document, for the first time, the integration of South Korean and US nuclear and conventional forces to include responses to North Korean nuclear actions."

The Defense Ministry pledged to "significantly enhance the alliance's readiness posture and capabilities by conducting exercises and training based on plans for conventional-nuclear integration."

The ministry also said, "The frequency and intensity of deployments of US (strategic) nuclear assets will be increased to a level comparable to a permanent presence, with corresponding exercises and training for South Korea-US conventional-nuclear integration conducted in conjunction with these deployments."