In late April 2023, the South Korean President Yoon made a state visit to the United States.
There he met with President Biden to discuss security policy in the Korean peninsula.
As part of this, President Yoon permitted the nuclear submarines of the US Navy to anchor
in South Korean waters, an arrangement unseen since the end of the Cold War.
Soon after, American officials announced that the U.S. Navy’s Ohio-class ballistic missile
submarines would undertake port visits to South Korea.
Reportedly, there will be no hard limit on the number of visitations going forward, or
even the potential for basing the submarines in South Korea.
The public nature of these visits marks a departure from the usual operational routine
of a ballistic missile submarine.
These types of submarines are supposed to stay hidden somewhere in the ocean, away from
prying eyes.
There they will wait for a certain signal, which will hopefully never be received.
This would be a grim order to unleash a nuclear attack authorized by none other than the President
of the United States.
Until that happens, a nuclear ballistic missile submarine, or in short SSBN, has only one
job: to remain undetected and to remain a threat, thereby influencing the decision-making
of other actors.
In this case however, US SSBNs are performing very public nuclear signalling to put overt
pressure on adversaries.
Sure enough, on 20 June, the Ohio class submarine, the USS Michigan arrived in the port city
of Busan, in South Korea.
However, do note that the USS Michigan is no longer classified as a SSBN, a nuclear
ballistic missile submarine.
It has actually been converted into SSGN, a guided missile submarine.
It is no longer supposed to have nuclear warheads, but in their place is a large number of land-attack
cruise missiles.
That said, both US and South Korean official stated that the deployment of a proper Ohio
class SSBN to South Korea will happen sometime in the near future.
This will be a proper doomsday submarine armed with enough weapons of mass destruction to
destroy entire nations.
Each Ohio-class SSBN was built to launch 24 Trident ballistic missiles while underwater.
The current variant of this missile family in service is the Trident II.
Each missile can, in turn, release up to 12 independent re-entry vehicles, each with the
ability to separately target and obliterate individual cities.
Each of these re-entry vehicles has 90 kilotons of TNT, six times the power of the nuclear
bomb dropped on Hiroshima.
However, due to the New START arms control treaty with Russia signed in 2010, the number
of active missile tubes on the Ohio-class SSBN was later reduced to 20, and each missile
is typically loaded with just four independent re-entry vehicles.
Nevertheless, this still represent an enormous amount of destructive potential.
For defensive measures against submarines and surface warships, the Ohio class has four
533-millimetre torpedo tubes.
This is similar to the torpedo armaments on the other two of the US Navy’s primary submarine
classes, the Improved Los Angeles and the Virginia classes.
They use the mark 48 Mod 7 heavyweight torpedoes, with a broadband advanced sonar system, and
the latest in a long evolution of the Mark 48 torpedo family.
The guided missile submarine conversion of the Ohio class has 154 tomahawk land-attack
missiles inside its missile tubes.
In some ways, the guided missile version of the class can be seen as more threatening
than the originals, if only because the threshold for using the Tomahawk missiles is far lower
than using the nuclear weapons, and there’s a lot of Tomahawks inside these subs.
The Ohio class is a massive submarine, displacing 18,750 tonnes submerged, with a length of
170 metres and a beam of 13 metres.
Because the Ohio is single-hulled, unlike the Russian and the Chinese submarines, it
can afford to be relatively narrow, without losing in terms of capabilities like rafting
and sound isolation, weapon storage and crew accommodation.
Her main powerplant is the General Electric S8G pressurised water reactor, which produces
steam that in turns powers two steam turbines rated at 70,000 shaft horse powers altogether.
She has a single 7-bladed propeller.
Reportedly, she has a speed of around 25 knots submerged.
She has a crew of 155, and being a nuclear boat, her range and underwater endurance is
only limited by food supplies.
The Ohio class SSBN doesn’t really need to be that close to unleash nuclear apocalypse
on their target.
A Trident II missile has a range exceeding 7,000 miles, meaning that a nuclear strike
launched from east of Hawaii can easily hit the entirety of North Korea, or even most
of China.
Indeed, the SSBN does not even need to leave its home base on the US West Coast.
So, there’s no real advantage from a nuclear deterrence perspective to base these submarines
close to North Korea and China.
In fact, making a publicised port visit removes any mystery around the submarines’ location.
In the event of a conflict, it exposes these submarines to be targeted and destroyed.
Even during peacetime, such a close deployment would risk giving away these submarines’
acoustic signature, helping the Chinese Navy to better detect and identify them going forward.
So, why would the US Navy take such extraordinary risk to deploy these subs in such a highly
publicised manner?
And the answer is of course that the SSBN port visit serves a political purpose.
Firstly, the deployment put pressure on America’s enemies, or more accurately the countries
that America perceives as her enemies.
The US hopes to discourage North Korea’s weapon development, and in particular the
testing of their nuclear weapon delivery systems, which have progressed rapidly in recent years
and are now able to hit the US mainland.
These include North Korea’s own ballistic missile submarines, their intercontinental
ballistic missiles that release multiple nuclear warheads, and hypersonic glide vehicles.
The SSBN port visit fits the well-established US tradition of show of force, which in the
past did not typically involve SSBN deployment.
In short, basing the SSBN close to North Korea sends a pointed warning at the country, even
through in practice the nuclear threat it poses is basically the same no matter where
it is in the Pacific.
The deployment can also be seen as a not-so-subtle message to China.
It’s a way for Washington to tell Beijing that the United States has the political capital
to base its nuclear weapons at China’s doorstep if it chooses to.
For now, there’s no confirmation that the submarines will be based in South Korea on
a long-term basis, but Washington is saying that it could be if we choose to.
The deployment may not actually raise the practical threat level posed by these submarines,
but they do raise the stakes and magnify the consequences if something goes wrong on the
Korean peninsula.
And instead of deterring North Korea from pursuing its weapon programme, it may incentivise
them to hurry up with developing their delivery system for nuclear warheads.
This would in turn contribute to the nuclearization of the Korean peninsula.
And of course, the deployment is not without risk to the US Navy.
Whatever the reasons may be for deployment, the SSBN port visit does expose the Ohio class
to detection by China’s rapidly growing submarine forces and surface anti-submarine
assets.
Both Chinese and North Korean naval forces will have ample opportunity to collect the
acoustic and electromagnetic signature of the vessel.
This may very well expose other vessels of the Ohio class to be more easily detected
and tracked by Chinese naval forces.
There is a growing consensus that China’s nuclear attack submarines are becoming more
and more capable over time, both in terms of lower noise levels and the sensitivity
of their sonar systems.
In a day and age where the US no longer has a commanding lead in submarine technology
over China, the deployment of one of their most important submarine classes so close
to China may easily backfire.
Despite the risk, the US is doubling down on the trend of publicising SSBN visits to
places like Guam, South Korea, and Gibraltar.
The White House wants to utilise the nuclear-signalling potential of the Ohio class doomsday submarines,
even at the risk of exposing more of the class to detection and potential destruction in
any future naval conflict.
And out of interest, let’s talk about the history of the Ohio class.
They were designed in the early 1970s to replace the Lafyette class of SSBNs.
At that time, the US Navy had already developed the Polaris submarine-launched ballistic missiles.
The Polaris was a reasonably effective missile.
It was compact enough to be stored in large numbers on the Lafyette class.
However, compared with later missiles, its range was limited, and it had to venture close
to the Soviet Union to maintain nuclear deterrence.
And here’s where the Ohio class came in.
The Ohio class was designed from the ground up to accommodate a long-range ballistic missile,
the Trident I, which was concurrently designed with the submarine.
Advances in noise reduction technology meant that the Ohio class was much quieter than
its predecessors.
The USS Ohio, the lead ship, was virtually undetectable in her sea trials in 1982.
So, at the time of their introduction, the class was among the quietest nuclear-powered
submarines in service.
A total of 18 boats were completed.
In 1994, the Nuclear Posture Review study determined that only 14 of the Ohio class
would be sufficient for the strategic nuclear posture of the United States.
A decision was made to convert four boats into guided missiles submarines, capable of
conducting conventional strikes against land targets.
So, 14 of the class continue to serve as ballistic missile subs, while 4 have been converted
into guided missile subs, including the aforementioned USS Michigan.
The Ohio class has one of the longest service lives out of all the Cold War era warships.
In fact, the longevity of USS Ohio is only matched by the oldest active carrier in the
US Navy, the USS Nimitz.
Nevertheless, the end of the road for the class is on the horizon.
Starting in 2031, they will be gradually replaced by the Columbia class SSBNs.
As China, the rising maritime power of the 21st century, begins to build advanced and
highly silent submarines, old vessels like the Ohio will be need to be phased out.
However, it remains unclear and indeed unconvincing whether American shipyards can build advanced
submarines fast enough to maintain the US Navy’s underwater advantage.