From deterrence to defense: The strategic implications of SDI

A game-theoretic model of the Strategic Defense Initiative, or "Star Wars," is developed based on a deterrence model founded on the game Chicken. In the Deterrence Game, the two players can choose any level of preemption, and threaten any level of retaliation against preemption, whereas in the Star Wars Game they are constrained in these choices by the defensive capabilities of an opponent. Nash equilibria, or stable outcomes, are derived in this game and illustrated for three different scenarios involving various postulated relationships between first-strike and second-strike defense. Mutual preemption can emerge as an equilibrium under SDI, underscoring the problem -- particularly if defensive capabilities are unbalanced -- that the development of Star Wars may subvert deterrence. Ramifications of this model for avoiding preemption and preserving crisis stability in superpower relations are discussed.