Third, there is a risk of asymmetrical challengers. Countries that fall behind in space weapon advancement may turn to using chemical or biological weapons. This may heighten the risk of escalation, bypassing any deterrent effects of nuclear weapons. Entanglements Cold-war bipolarity no longer is applicable to the global power balance. The complex modern alliance system makes allies and enemies tied to one another. Thus, action by one country to deter another could threaten the safety of a third country. “Security trilemmas” could increase tension during mundane acts of cooperation, complicating MAD. Emerging hypersonic weapons Hypersonic ballistic or cruise missiles threaten the retaliatory backbone of mutual assured destruction. The high precision and speed of these weapons may allow for the development of "decapitory" strikes that remove the ability of another nation to have a nuclear response. In addition, the secretive nature of these weapons' development can make deterrence more asymmetrical. Failure to retaliate If it was known that a country's leader would not resort to nuclear retaliation, adversaries may be emboldened. Edward Teller, a member of the Manhattan Project, echoed these concerns as early as 1985 when he said that "The MAD policy as a deterrent is totally ineffective if it becomes known that in case of attack, we would not retaliate against the aggressor." See also Absolute war Appeasement Balance of terror Counterforce Crab mentality Game theory Lam chau (doctrine) Letters of last resort Moral equivalence Nuclear winter Nuclear missile defense Nuclear holocaust Nuclear peace Nuclear strategy Pyrrhic victory Rational choice theory Samson Option The war to end war Weapon of mass destruction References External links "The Rise of U.S. Nuclear Primacy" from Foreign Affairs, March/April 2006 First Strike and Mutual Deterrence from the Dean Peter Krogh Foreign Affairs Digital Archives Herman Kahn's Doomsday Machine Robert McNamara's "Mutual Deterrence" speech from 1967 Getting MAD: Nuclear Mutual Assured Destruction Center for Arms Control and Non-Proliferation Council for a Livable World Nuclear Files.org Mutual Assured Destruction John G. Hines et al. Soviet Intentions 1965–1985. BDM, 1995. Cold War policies Nuclear strategy Nuclear weapons Nuclear warfare English phrases Military doctrines Cold War terminology Nuclear doomsday Theories of history