By Brad Lendon, CNN
When the presidents of the United States and South Korea this week announced a landmark deal to deter North Korean aggression, one element of the pact stood out.
Plans to deploy a US nuclear-armed submarine South Korea for the first time since 1981 were the lead act in unveiling the “Washington Declaration,” a set of measures intended to make Pyongyang think twice before launching a nuclear attack on its southern neighbor.
“Our mutual defense treaty is unbreakable and that includes our commitment to extend deterrence, and that includes the nuclear threat, nuclear deterrence,” US President Joe Biden said at a White House news conference with South Korean President Yoon Suk Yeol. .
But while the measure has enormous symbolic value, some experts question whether it makes sense as a military measure. Some point out that the submarines are quite capable of attacking North Korea from thousands of kilometers away; Others argue that sending the sub on a visit to a very public, foreign port only compromises the effectiveness of a weapon designed for stealth.
Here’s what you need to know about the submarine and why it’s headed for South Korea.
It’s called ‘boom’
The US Navy has 14 Ohio-class nuclear-powered ballistic missile submarines (SSBNs), eight based in Washington state and six based in Georgia.
The 560-foot submarines, commonly called “boomers,” have a displacement of more than 18,000 tons when submerged and are each powered by a single nuclear reactor.
The Navy says an Ohio-class submarine is designed to spend an average of 77 days at sea, followed by 35 days in port for maintenance. Submarines have two crews each, referred to as the “blue” and “gold” crews, and these rotate for the 155 divers in each crew to rest and train properly between patrols.
What weapons do they carry?
Each of the Ohio-class submarines carries a maximum of 20 Trident II ballistic missiles.
These have a range of 4,600 miles (7,400 kilometers), meaning they are capable of hitting a target in North Korea from vast swaths of the Pacific, Indian or Arctic oceans.
“Militarily, (these submarines) don’t need to be anywhere near Korea to hit potential targets there,” said Blake Herzinger, a researcher at the US Center for Studies.
Each Trident missile is capable of carrying multiple warheads. youhat can be directed towards separate targets.
The James Martin Center for Nonproliferation Studies Nuclear Threats Initiative estimates that each Trident missile can carry four nuclear warheads, meaning that each US ballistic missile submarine could carry about 80 nuclear warheads.
In other words, a single Trident-armed submarine could destroy all of North Korea.
Why send one to South Korea?
Analysts say the presence of a US Navy ballistic missile submarine in a South Korean port would be purely symbolic and would actually reduce the submarine’s military value.
“Tactically, (the US and South Korea) are diminishing the most powerful asset of the submarine; their stealth,” said Carl Schuster, a former US Navy captain and former director of operations at the US Pacific Command Joint Intelligence Center in Hawaii.
One of the keys to nuclear deterrence is uncertainty.
“Nuclear deterrence requires that while the adversary knows of the existence and scale of state nuclear weapons, it cannot know the exact range or location of the capabilities or when they might be employed,” US Navy Cmdr. USA Daniel Post wrote in the journal Proceedings of the US Naval Institute. in January.
A US ballistic missile submarine lurking hundreds of feet below the ocean surface thousands of miles from North Korea would still be within Pyongyang’s range, but nearly impossible for North Korea to detect.
One arriving in South Korea on a port visit, which must be arranged 24 to 48 hours in advance, would be much more visible, giving North Korea an advantage, Schuster said.
“If Kim Jong Un was looking to do a surprise attack, we gave him the location of the submarine and the time it will be there,” Schuster said.
The United States wants to reassure one of its most important allies that it is behind it, analysts say.
Kim Jong Un has been building North Korea’s nuclear-capable missile forces, testing them at a record pace by 2022. And in a New Year’s Eve speech, the The North Korean leader called for an “exponential increase” in his country’s arsenal of nuclear weapons. in response to what he claims are threats from South Korea and the United States.
Kim’s threats have led some in South Korea to call for Seoul to become a nuclear-armed power. The United States does not want to see a nuclear proliferation on the peninsula, so it has been trying to reassure its ally by making its forces more visible in the area, including flying nuclear-capable B-52 bombers in the skies around South Korea.
Kim Jung-sup, a senior fellow at the Sejong Institute’s Center for Defense Studies in Seoul, said the submarines simply emphasize that point and increase the credibility of the United States.
“Of course, they are different types of weapons, but I don’t think there is an essential difference in the fact that they are strategic assets that fundamentally send a message of nuclear retaliation against North Korea,” Kim said.
As for making US submarines vulnerable, some analysts say such a scenario would only occur as a precursor to nuclear war, by which time the submarine would have already failed its key deterrent mission.
“Their fundamental purpose is to deter and reassure,” said Drew Thompson, a senior fellow at the Lee Kuan Yew School of Public Policy at the National University of Singapore.
“Strategic weapons like a ballistic missile submarine and its payload are not meant to be used.”
The CNN Wire
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CNN’s Gawon Bae contributed to this report.