(all quotes unless otherwise stated are from the NYT)
South Korea has a problem and the United States has a problem in the Korean peninsula.
The United States does not want to have a nuclear arms race happen in Southeast Asia and particularly not on the Korean peninsula. It is for that reason that the United States has always assured Seoul that they would guarantee protection over South Korea from any threats out of North Korea.
When the United States notified the South Korean administration of its plan to withdraw USFK in July 1970, South Korea first considered the possibility of an independent nuclear program. Under the direction of South Korea's Weapons Exploitation Committee, the country attempted to obtain plutonium reprocessing facilities following the pullout of the 26,000 American soldiers of the 7th Infantry Division in 1971.
However, under pressure from the United States, France eventually decided not to deliver a reprocessing facility to South Korea in 1975.South Korea's nuclear weapons research program effectively ended on April 23, 1975 with its ratification of the Nuclear Non-Proliferation Treaty.
South Korea has the raw materials and equipment to produce a nuclear weapon but has not. In August 2004, South Korea revealed the extent of its highly secretive and sensitive nuclear research programs to the IAEA, including some experiments which were conducted without the obligatory reporting to theInternational Atomic Energy Agency (IAEA) called for by South Korea's safeguards agreement.The failure to report was reported by the IAEA Secretariat to the IAEA Board of Governors; however, the IAEA Board of Governors decided to not make a formal finding of noncompliance. If the South created nuclear weapons it could change the balance of power on the Korean peninsula. However, South Korea has continued on a stated policy of non-proliferation of nuclear weapons and has adopted a policy to maintain a nuclear-free Korean Peninsula.
Like Japan, South Korea has the raw materials, technology, and resources to create nuclear weapons. Previous incidents show the Republic of Korea (ROK) to be able to possess nuclear weapons in anywhere from one to three years if necessary.
The ROK has been shown before to create enriched uranium up to 77%, which although not particularly powerful, shows that South Korea has the potential to make nuclear weapons with more highly enriched uranium.
South Korea does not have any ICBMs but possesses a wide range of SRBM and MRBMs through the Hyunmoo series of ballistic/cruise missiles currently fielded to the ROK Army. The Hyunmoo series of ballistic missiles works similarly to the American Tomahawk Missile, which can be armed with the W80 and W84 nuclear warheads.
Theoretically, if needed, the 500 kg conventional warhead could be replaced by a small nuclear warhead. The Hyunmoo missiles can already cover the entire range of North Korea and would drastically change the North's disposition if the South had nuclear armed MRBMs. Even though the ROK could procure nukes, currently like Japan it sees no reason to do so with the protection of the American nuclear arsenal.
But now that North Korea has nuclear weapons and seems on track to be able to threaten North America in order to deter the United States from attacking North Korea either pre-emptively or in response to North Korean attacks on Seoul,Japan or Guam - there is a question - would the US risk one of its own cities and population to fulfill that promised guarantee? And with Trump's "America First and Only " mindset,that question gains substance.
After North Korea tested two intercontinental ballistic missiles in July, including one that appeared capable of hitting the mainland United States, South Koreans are not so sure the Americans would follow through.
“Would the Americans intervene in a war on the peninsula if their own Seattle were threatened with a North Korean nuclear ICBM?” said Park Hwee-rhak, a military analyst at Kookmin University in Seoul.
Like any country that faces an imminent threat from their neighbors,Seoul must balance depending upon a larger protector and having a back up plan in case that protector does not come through.
They must also maintain a razor's edge of being enough of a threat to their neighbor that the neighbor is deterred from attacking them but without provoking an attack from that neighbor by acting too much of a threat themselves.
Especially if that neighbor has nuclear weapons and you don't.
The worst case scenario would be for both North and South Korea to have nuclear weapons and uncertainty by both governments as to U.S. intentions and one of those three governments getting itchy fingers because everyone is ginning things up for political reasons and we all accidentally trip into World War Three.
The best case scenario is if North and South Korea enter into substantive talks and find some way to co-exist without extreme threats.
It is a difficult balancing act, pitting Mr. Moon’s preference for a diplomatic solution against his nation’s need to answer an existential question: How can a country without nuclear weapons deter a dictator who has them?
“The best deterrence we can have, next to having our own nukes, is to make Kim Jong-un fear for his life,” said Shin Won-sik, a three-star general who was the South Korean military’s top operational strategist before he retired in 2015.
The Korean public is growing increasingly unwilling to not take action on its own against North Korea's repeated provocations. They are spurred on by the more aggressive conservative opposition party that was just voted out of power (not over a difference of philosophy with the party's more hawkish stances,but as a reaction to scandal by the former President that culminated this spring in the election of President Moon's liberal party).
One of those hawkish voices belongs to Mr. Moon's Defense Minister.
Balancing that is Mr.Moon's stated intention to seek diplomatic means over military ones to resolve this eternal dilemma.
“The balance of terror is the shortest cut to deterring war,” Yoon Sang-hyun, a conservative opposition lawmaker, told Parliament last Tuesday.
Although a majority of South Koreans, especially conservative politicians and commentators, call for arming their country with nuclear weapons of its own, Mr. Moon has repeatedly vowed to rid the Korean Peninsula of such weapons.
As part of South Korea's efforts to deter North Korea without the luxury of having its own nuclear weapons,South Korea is specifically trying to make Kim Jong-un nervous on a personal level.
South Korean defense minister, Song Young-moo, told lawmakers in Seoul that a special forces “decapitation unit” would be established by the end of the year.
The brigade-size unit would operate officially. The military has been retooling helicopters and transport planes to penetrate North Korea at night so that the forces, known as the Spartan 3000, can carry out raids.
Rarely does a government announce a strategy to assassinate a head of state, but South Korea wants to keep the North on edge and nervous about the consequences of further developing its nuclear arsenal. At the same time, the South’s increasingly aggressive posture is meant to help push North Korea into accepting President Moon Jae-in’s offer of talks.
The measures have also raised questions about whether South Korea and the United States, its most important ally, are laying the groundwork to kill or incapacitate Mr. Kim and his top aides before they can even order an attack.
While Secretary of State Rex W. Tillerson has said the United States does not seek leadership change in North Korea, and the South Koreans say the new military tactics are meant to offset the North Korean threat, the capabilities they are building could be used pre-emptively.
South Korea's military knows such an operation is not feasible on a practical basis. But in addition to hoping it has an effect on Kim Jong-un,they are also using this exercise to fulfill another goal - increasing their heavy conventional arsenal to protect themselves regardless of US response to North Korea,keeping the US engaged without having US/Trump create a situation that lands South Korea in the middle of a hot conflict South Korea does not want and as a way to reassure its own population without the public becoming either so fearful or so bent on more aggressive actions that they oust Mr. Moons government and put in a more conservative hawkish government.