US nuclear-armed submarine heads to South Korea for first visit in 40 years

For the first time since the 1980s a US Navy nuclear-armed ballistic missile submarine (SSBN) will visit South Korea to help show Washington's resolve to protect the country from a North Korean attack.

The visit was announced in a joint declaration when South Korean President Yoon Suk-yeol and US President Joe Biden met in Washington on Wednesday.

Because US SSBNs rely on secrecy and stealth to ensure their survival and preserve their ability to launch nuclear missiles in a war, they rarely make public stops in foreign ports.

“That could be a huge pressure on North Korea, because usually they don’t share where those submarines are,” said Moon Keun-sik, a retired South Korean submarine captain and squadron leader.

The US has pledged to deploy more “strategic assets” such as aircraft carriers, submarines, and long-range bombers to South Korea to deter North Korea, which has developed increasingly powerful missiles that can hit targets from South Korea to the mainland US.

The submarine visit is also seen as a way to reassure South Korea and quell talk in Seoul of developing is own nuclear weapons.

“If a US SSBN visits and docks in South Korea, that is very unusual and symbolic ... the US wants to show it is going for stronger deterrence in a visible way and to calm South Koreans' concern,” said Choi Il, another retired South Korean submarine captain.

Pyongyang has condemned recent deployment of US aircraft carriers and joint South Korea-US military drills as proof of the allies’ hostile intent.

The US Navy fields 14 SSBNs, often referred to as “boomers”. Each Ohio-class submarines carries 20 Trident II D5 missiles, each of which can deliver up to eight nuclear warheads to targets as far as 12,000km away.

SSBNs often visited South Korea in the 1970s, when South Korea was debating the strength of US commitment and the need for its own nuclear arsenal, according a Federation of American Scientists report.

“For a few years the boomers arrived at a steady rate, almost every month, sometimes two-three visits per month,” wrote the report’s author, Hans Kristensen. “Then, in 1981, the visits stopped and the boomers haven’t been back since.”

No further details were provided about the latest visit but the declaration said it would be evidence of US commitment to “further enhance the regular visibility of strategic assets to the Korean Peninsula”.

A senior US official, speaking on condition of anonymity, told reporters  the visit would be part of more frequent trips to the peninsula by strategic assets, but that there is “no vision for any regular stationing or basing of those assets and certainly not nuclear weapons” in South Korea.

Reuters