For those interested in why some states seek nuclear weapons while others foreswear them, the Korean Peninsula presents an interesting case study. Both South Korea and North Korea have sought nuclear weapons; however, Seoul would abandon its nuclear pursuit while Pyongyang continues on a nuclear trajectory.
Why did they take such different nuclear paths? I would argue that this is best explained by the shifting conventional military balance on the Korean Peninsula between the 1960s and today.
Despite some earlier very basic atomic research activities, North Korea’s nuclear program didn’t start making much progress until the late 1970s, when it expanded its atomic cooperation with the Soviet Union. Nonetheless, it was during the 1980s and early 1990s when North Korea made the bulk of its indigenous nuclear progress. Indeed, by the time the first North Korean nuclear crisis ended in 1994, many believed that Pyongyang had enough reprocessed plutonium for a couple of nuclear devices.
What changed in the 1980s and 1990s to spur such sudden and rapid progress on North Korea’s nuclear program? One certainly cannot argue that the nuclear threats that North Korea faced expanded during this time. By the 1980s, the U.S. had been reducing the number of nuclear warheads it keep in South Korea for decades, and in 1991 it removed them all from the Korean peninsula. Moreover, South Korea had seriously explored a nuclear weapons program during the late 1960s and the 1970s. By the early 1980s, however, it had largely abandoned this course.
By contrast, during the 1980s and early 1990s, the conventional military balance on the Korean Peninsula shifted dramatically against North Korea. To begin with, the 1980s saw North Korea’s main patron, the Soviet Union, enter into a period of rapid decline. Its commitment to North Korea’s security also suffered during this time because the Soviet Union was tied down in Afghanistan and, later on, in Eastern Europe and the Soviet Union proper. Moscow’s declining commitment to Pyongyang is reflected in Soviet aid flows to North Korea. In 1980, the Soviet Union was still providing North Korea with $260 million of annual aid, as well as the “friendship prices” it offered Pyongyang on crucial imports. (These friendship prices were substantial. In 1988, for example, the Soviet Union was estimated to have shipped $1.9 billion of goods to North Korea and received just $900 million in payments). Just seven years later, in 1987, North Korea was running a deficit with the Soviet Union. Three years later, all Soviet aid to North Korea stopped. Moreover, during the late 1980s and early 1990s, the Soviet Union and China both established diplomatic relations with Pyongyang’s arch enemy, South Korea.
Equally important, the inter-Korean conventional military balance shifted in Seoul’s favor during this time period because of South Korea’s rapid economic growth. As North Korea’s invasion of South Korea in 1950 demonstrated, in the early Cold War the military balance between the two Koreas greatly tilted toward the North. This continued to be the case for the next few decades. Indeed, before the mid-1970s, North Korea’s economy was larger than South Korea’s. This was especially true in per capita terms, given that South Korea has a much larger population. Consequentially, even in the mid-1970s when South Korea’s GDP reached parity with North Korea’s, Pyongyang remained wealthier and therefore able to devote more resources to the military. Indeed, between the mid-1960s and mid-1970s, North Korea devoted between 15-20% of its GDP to the military while Seoul was spending just 5% of its own. As a result, according to Scott Snyder, North Korea’s military was estimated to be twice as strong as South Korea’s armed forces during the 1970s.
However, South Korea’s continued robust economic growth rates after the mid-1970s rapidly widened the gap between North Korea and South Korea. Thus, from reaching parity in the mid-1970s, South Korea’s economy was at least seven times larger than North Korea’s by 1988. By 1994, even North Korea’s per capita GNP was eight times lower than South Korea’s. South Korea’s technological superiority over the North also grew substantially during this time, with all the implications this had for the military balance. Thus, given the enormous shift in the conventional balance of power in the Korean Peninsula in the 1980s and 1990s, as well as Pyongyang’s loss of a great power patron, it’s not surprising that North Korea pursued nuclear weapons. How else could it have deterred a South Korea and/or U.S. attack?
This background also has interesting implications for South Korea’s nuclear trajectory, which is almost a perfect mirror image of its northern neighbor. South Korea became interested in atomic energy in the 1950s as a potential way to mitigate its energy insecurity. However, in the very late 1960s and especially the 1970s, South Korea made a viable effort to acquire a nuclear weapons. For example, in 1971 President Park initiated a nuclear weapons program and created a high-level coordinating committee called the Weapons Exploitation Committee (WEC). He also ordered the Korea Atomic Energy Research Institute (KAERI) to acquire reprocessing capabilities, and began secretly budgeting the nuclear weapons effort to shield them from the National Assembly and public. In the following years, South Korea began trying to acquire the necessary technologies for a nuclear weapons program from foreign countries like France, Belgium and Canada. These efforts were discovered by the U.S., however, who brought strong pressure to bear on South Korea and the countries Seoul was courting for nuclear technology. Thus, by the early 1980s, South Korea had almost entirely abandoned its nuclear pursuit. It has remained a peaceful nuclear power ever since.
Nuclear threats and America’s extended deterrence cannot explain this trajectory. After all, South Korea abandoned its nuclear program at the same time that the nuclear threats it faced grew, and U.S. extended deterrence weakened. As noted above, North Korea began its nuclear weapons program in earnest in the same decade Seoul shuttered its own. As also noted above, North Korea’s nuclear weapons program expanded at the same time that the U.S. was withdrawing forwarded deployed nuclear warheads from South Korea. Still, despite the absence of U.S. forward deployed nuclear weapons in South Korea, as well as North Korea’s eventual acquisition of a nascent nuclear capability, South Korea has continued to abstain from nuclear weapons.
As was the case with North Korea, South Korea’s nuclear trajectory is best explained by the shifting conventional military balance on the Korean Peninsula. Although South Korea’s military was much weaker than North Korea’s through at least the end of the 1970s, it compensated for this by having a strong military alliance with the United States, which included a large forward deployed U.S. military force along the 38th Parallel. However, under pressure because of the Vietnam War, President Richard Nixon announced the Guam Doctrine in a speech in that territory in 1969.
The Guam Doctrine, which later became known as the Nixon Doctrine, stated that the U.S. would keep its treaty commitments to allies, and that it would still provide extended deterrence to allies and partners to deter nuclear attacks against them. However, Nixon also stated that in cases of non-nuclear aggression, “we shall look to the nation directly threatened to assume the primary responsibility of providing the manpower for its defense.” This was followed by a period of significant U.S. troop reductions in South Korea. Whereas over 66,000 U.S. troops were stationed in South Korea in 1969, only around 40,000 troops remained in the country by 1971. Moreover, in 1976, President Jimmy Carter called for further reductions in U.S. troops in the Republic of Korea.
Not surprisingly, all of this led President Park to question America’s willingness to defend his country if North Korea invaded again. Since South Korea couldn’t compete with North Korea’s conventional military power at the time, it sought nuclear weapons to deter an invasion. However, as the conventional military balance shifted in South Korea’s favor in the 1980s and 1990s, this rationale for seeking nuclear weapons diminished.
It had shifted so dramatically by the first decade of the 21st century that even North Korea’s nuclear tests in 2006, 2009 and 2013 haven’t shaken South Korea’s nuclear forbearance. Instead, Seoul has responded to North Korea’s growing nuclear capabilities in two ways. First, it has sought greater reassurances from the United States about its extended deterrence policies in the Asia-Pacific. Second, it is pursuing the necessary military capabilities—such as ISR, precision-strike, and missile defense—to preemptively destroy North Korea’s nuclear arsenal under the doctrine of “active deterrence.”