Book Manuscript
- Tailoring Extended Deterrence: How States Provide the Security Umbrella
Abstract: Nuclear patrons extend deterrence to other non-nuclear clients for 1) deterring potential aggressors from attacking the clients; and 2) assuring the clients of their security. For the dual goals, nuclear patrons have employed different strategies across disparate clients. Besides, their strategy for the same client’s protection has varied over time.
For example, over the last 70 years since the formation of North Atlantic Treaty Organization (NATO), the US security commitment to NATO-Europe has relied on forward-deployed nuclear weapons coupled with large-scale conventional troops in the European continent. Although the US extended deterrence over South Korea has remained at a nuclear-level as well, it underwent a considerable change in the early 1990s. That is, America’s preexisting on-shore nuclear umbrella shifted to an offshore nuclear shield. In contrast, the US extended deterrence to the Philippines during the Cold War was conventional: the US prepositioned robust conventional troops in the Archipelago, and it did not publicly make any nuclear commitment or openly employ nuclear assets for the client’s protection.
In short, the security umbrellas provided have not been one-size-fits-all. Instead, they have been tailored to individual clients’ unique security needs and circumstances. However, we still do not have a systematic framework to understand how nuclear patron states provide a security umbrella for nonnuclear states. What extended deterrence strategies are available to nuclear patrons and what factors determine which strategy they will adopt (strategy adoption)? How are the individual strategies embodied as actual force employment (strategy implementation)? This study aims to answer the questions by identifying the divergent causal paths that lead patrons to develop a distinct extended deterrent posture over time and across clients.
With regards to the question of strategy adoption, I argue that the interplay of two variables—1) the type of threat posed by an enemy to a client and 2) the likelihood of an enemy’s quick victory in the event of war with a client—determines which of four distinct strategies a nuclear patron will adopt: “forward nuclear deployment,” the “nuclear defense pact,” “forward conventional deployment,” and the “conventional defense pact.” Regarding the threat variable, I distinguish between two types of threats—existential and non-existential—determined by the enemy’s claimed goal in conflict with a client. With regards to the quick-victory variable, I distinguish between two possibilities—high and low—determined by the enemy’s surprise and mobile warfare capability vis-à-vis a client.
The type of threat posed by an enemy to a client determines a patron’s required level of security commitment to assure the client—whether nuclear or conventional level. The likelihood of an enemy’s swift overrun of a client affects the location of a patron’s prepositioned forces to deter the enemy—whether forward or rear. The interaction of two dichotomous variables generates a set of extended deterrence strategies, creating four testable hypotheses as follows.
First, when a patron judges that a client faces an existential threat (e.g. a threat of entire political absorption) and an enemy’s quick victory is highly likely, a patron will adopt a “forward nuclear deployment” strategy. Second, when a client is under an existential threat and an enemy’s swift victory seems unlikely, a patron will adopt a “nuclear defense pact” strategy. Third, when a client is faced with merely a non-existential threat (e.g. a threat of territorial annexation) and an enemy’s swift overrun of a client is likely, a patron will adopt a “forward conventional deployment” strategy. Finally, when a client faces a non-existential threat and an enemy’s swift victory seems unlikely, a patron will adopt a “conventional defense pact” strategy.
With regards to the question of strategy implementation, I argue that each strategy is characterized by a unique mix of conventional and nuclear assets prepositioned in either forward or rear areas. “Forward nuclear deployment” is embodied as the combination of on-shore tactical nuclear weapons and substantial conventional shield troops along the frontline. Second, a “nuclear defense pact” is comprised of off-shore strategic nuclear forces coupled with conventional token forces in the rear area of the client’s soil. Third, “forward conventional deployment” is manifested as sizable conventional frontline troops, but an absence of any prepositioned nuclear assets. Lastly, a “conventional defense pact” contains neither conventional nor nuclear forward military presence.
To substantiate my argument, I examine four cases of extended deterrence: 1) US extended deterrence to NATO-Europe, 2) US extended deterrence to South Korea, 3) US extended deterrence to the Philippines, and 4) Soviet extended deterrence to Mongolia.
Working Papers
- "The Strategic Logic of Advanced Nuclear Transfer"
- "Searching for Nuclear Superiority: Nuclear Offensive Capabilities and Crisis Outcomes (with Jiyoung Ko)"
- "Why are They Still There?: Explaining the US Forward-Deployed Nuclear Weapons in Europe since 1991"
- "Time-Horizons and Alliance Cohesion"
- Tailoring Extended Deterrence: How States Provide the Security Umbrella
Abstract: Nuclear patrons extend deterrence to other non-nuclear clients for 1) deterring potential aggressors from attacking the clients; and 2) assuring the clients of their security. For the dual goals, nuclear patrons have employed different strategies across disparate clients. Besides, their strategy for the same client’s protection has varied over time.
For example, over the last 70 years since the formation of North Atlantic Treaty Organization (NATO), the US security commitment to NATO-Europe has relied on forward-deployed nuclear weapons coupled with large-scale conventional troops in the European continent. Although the US extended deterrence over South Korea has remained at a nuclear-level as well, it underwent a considerable change in the early 1990s. That is, America’s preexisting on-shore nuclear umbrella shifted to an offshore nuclear shield. In contrast, the US extended deterrence to the Philippines during the Cold War was conventional: the US prepositioned robust conventional troops in the Archipelago, and it did not publicly make any nuclear commitment or openly employ nuclear assets for the client’s protection.
In short, the security umbrellas provided have not been one-size-fits-all. Instead, they have been tailored to individual clients’ unique security needs and circumstances. However, we still do not have a systematic framework to understand how nuclear patron states provide a security umbrella for nonnuclear states. What extended deterrence strategies are available to nuclear patrons and what factors determine which strategy they will adopt (strategy adoption)? How are the individual strategies embodied as actual force employment (strategy implementation)? This study aims to answer the questions by identifying the divergent causal paths that lead patrons to develop a distinct extended deterrent posture over time and across clients.
With regards to the question of strategy adoption, I argue that the interplay of two variables—1) the type of threat posed by an enemy to a client and 2) the likelihood of an enemy’s quick victory in the event of war with a client—determines which of four distinct strategies a nuclear patron will adopt: “forward nuclear deployment,” the “nuclear defense pact,” “forward conventional deployment,” and the “conventional defense pact.” Regarding the threat variable, I distinguish between two types of threats—existential and non-existential—determined by the enemy’s claimed goal in conflict with a client. With regards to the quick-victory variable, I distinguish between two possibilities—high and low—determined by the enemy’s surprise and mobile warfare capability vis-à-vis a client.
The type of threat posed by an enemy to a client determines a patron’s required level of security commitment to assure the client—whether nuclear or conventional level. The likelihood of an enemy’s swift overrun of a client affects the location of a patron’s prepositioned forces to deter the enemy—whether forward or rear. The interaction of two dichotomous variables generates a set of extended deterrence strategies, creating four testable hypotheses as follows.
First, when a patron judges that a client faces an existential threat (e.g. a threat of entire political absorption) and an enemy’s quick victory is highly likely, a patron will adopt a “forward nuclear deployment” strategy. Second, when a client is under an existential threat and an enemy’s swift victory seems unlikely, a patron will adopt a “nuclear defense pact” strategy. Third, when a client is faced with merely a non-existential threat (e.g. a threat of territorial annexation) and an enemy’s swift overrun of a client is likely, a patron will adopt a “forward conventional deployment” strategy. Finally, when a client faces a non-existential threat and an enemy’s swift victory seems unlikely, a patron will adopt a “conventional defense pact” strategy.
With regards to the question of strategy implementation, I argue that each strategy is characterized by a unique mix of conventional and nuclear assets prepositioned in either forward or rear areas. “Forward nuclear deployment” is embodied as the combination of on-shore tactical nuclear weapons and substantial conventional shield troops along the frontline. Second, a “nuclear defense pact” is comprised of off-shore strategic nuclear forces coupled with conventional token forces in the rear area of the client’s soil. Third, “forward conventional deployment” is manifested as sizable conventional frontline troops, but an absence of any prepositioned nuclear assets. Lastly, a “conventional defense pact” contains neither conventional nor nuclear forward military presence.
To substantiate my argument, I examine four cases of extended deterrence: 1) US extended deterrence to NATO-Europe, 2) US extended deterrence to South Korea, 3) US extended deterrence to the Philippines, and 4) Soviet extended deterrence to Mongolia.
Working Papers
- "The Strategic Logic of Advanced Nuclear Transfer"
- "Searching for Nuclear Superiority: Nuclear Offensive Capabilities and Crisis Outcomes (with Jiyoung Ko)"
- "Why are They Still There?: Explaining the US Forward-Deployed Nuclear Weapons in Europe since 1991"
- "Time-Horizons and Alliance Cohesion"
* Header image: NATO Headquarters in Brussels, Belgium. (Photo from NATO website)