The U.S. Nuclear Umbrella over South Korea: Nuclear Weapons and Extended Deterrence

For more than 60 years, the United States has maintained an extended deterrence commitment to protect South Korea as part of a system of alliances in East Asia. The guarantee included a mutual security treaty that formalized the U.S. pledge to defend its ally and placed troops along the demilitarized zone (DMZ) as a sign of the U.S. determination to defend South Korea. The U.S. commitment also entailed South Korea’s inclusion under the U.S. nuclear umbrella, whereby Washington vowed to use nuclear weapons to deter and, if need be, defeat an attack on the South. The nuclear umbrella included the deployment of tactical nuclear weapons on the peninsula; however, these were removed in 1991. Despite the longevity of U.S. extended deterrence and the nuclear umbrella in East Asia, there have always been some difficult and troubling aspects of this strategy. An important requirement for successful deterrence is credibility. Would the United States truly be willing to use nuclear weapons in the defense of an ally given the tremendous devastation of those weapons? What if the adversary possessed nuclear weapons that could strike the U.S. homeland or U.S. facilities in the region? Would the United States use nuclear weapons in response to a non-nuclear attack, whether conventional, biological, or chemical? Indeed, some even question whether there is a nuclear umbrella.