By Josh Smith
SEOUL (Reuters) – When a U.S. ballistic missile submarine (SSBN) surfaced for a rare visit to South Korea this week, it was a stark reminder that Washington has always deployed nuclear-tipped missiles in close proximity to North Korea, analysts said.
Some analysts said having nuclear weapons out of sight in the seas off the Korean peninsula was a potentially stronger deterrent for the North than planting them in South Korea, as Washington had done from 1958 to 1991.
“Placing nukes offshore and on submarines is actually a stronger deterrent in many ways,” said Duyeon Kim of the Center for a New American Security. “Deterrence is enhanced when the location of US strategic assets is unknown to the adversary so long as the adversary knows these weapons exist.”
The USS Kentucky Ohio-class SSBN arrived in South Korea’s southern port of Busan on Tuesday and ended its visit on Friday, a source with direct knowledge of its movements said.
This caught the attention of North Korea.
On Thursday, North Korea’s defense minister said the mere presence of such weapons in South Korea could meet the criteria for the North to use its nuclear weapons, and warned the United States against sending other nuclear-capable assets.
Kentucky’s visit was the first by an SSBN to South Korea since the 1980s, and it follows growing debate in recent years over whether the United States should return tactical nuclear weapons to South Korea or whether it should develop its own.
Reassuring of its commitment to defend the South, Washington responded by stepping up displays of nuclear force and creating a new war planning group.
China, the North’s most important ally, did not comment on the submarine’s visit, but accused the United States of increasing tension in the region with its military deployments.
ALWAYS WITHIN REACH
Because US SSBNs rely on secrecy and stealth to ensure their survival and preserve their ability to launch nuclear missiles during a war, they rarely make public calls at foreign ports.
SSBNs are the most resilient delivery platform of any US nuclear weapon, essentially guaranteeing crushing nuclear retaliation in the event of an enemy first strike, said Vann Van Diepen, a former US government weapons expert who works with Project 38 North which monitors North Korea.
The US Navy has 14 SSBNs, often called “boomers”. An Ohio-class submarine carries 20 Trident II D5 missiles, each capable of delivering up to eight nuclear warheads to targets 12,000 km (7,500 miles) away.
“American SSBNs anywhere from the west coast of the United States to the west can hit targets in North Korea,” Van Diepen said. “Therefore, some US SSBNs are within range of North Korea at all times.”
North Korea has a large but aging submarine force whose primary mission is to defend its coastline, but is seeking to develop its own arsenal of missile submarines.
It has conducted launches from a test submarine and has sought to build an operational missile submarine since at least 2016, Van Diepen said.
But the North is many years away from developing the technical capability to build a nuclear-powered submarine that would give it unlimited autonomy, he said. For now, a missile submarine would only marginally complement the North’s burgeoning land-based nuclear force, Van Diepen said.
“The de facto nuclear sharing between the United States and South Korea is underway,” said Choi Il, a retired South Korean submarine captain.
“The port of Kentucky stopover in Busan tells us that the submarine has previously operated in waters around the Korean Peninsula and even after leaving Busan, US nuclear assets are still deployed in nearby waters.”
(Reporting by Josh Smith; Additional reporting by Ju-min Park; Editing by Simon Cameron-Moore)