The Trump administration announced its new nuclear strategy earlier in the month of February. The plan aims to match any and all movement made by Russia to modernize their forces--as long as it stays within the boundaries of treaties. In the beginning of March, Russian President Vladmir Putin announced that Russia had new nuclear-capable weapons which make nuclear defense systems “useless.”
The escalating rhetoric and planned nuclear build-up by the United States might lead one to question the necessity of some of the planned expenditures. The Nuclear Posture Review had called for the fitting of Trident II missiles with low-yield nuclear warheads. Many believe that this is the best and most humane way to counter the escalation of Russian deployment of low-yield nuclear warheads. However, in accordance with nuclear deterrence theory, the possession or use of low yield nuclear undermines security. If a state possesses low yield nuclear weapons this indicates that they intend to be used, as nuclear weapons serve the singular purpose of preventing the use of nuclear weapons. And there can only be two results coming from the use of low-yield nuclear weapons.
First, the use of a single low-yield nuclear weapon utilized against a nuclear power would trigger a second-strike. According to the theory, a second-strike will likely be the entirety of the targeted state's nuclear arsenal, as they must make it impossible for there to be a third strike. Thus, it is imperative that the targeting nation inflict so much damage that a second strike is no longer possible. For this reason, low-yield nuclear weapons are ineffective against nuclear powers beyond deterring the use of nuclear weapons.
Second, the use of a low-yield nuclear weapon would trigger new nuclear arms race if used against a non-nuclear power. An attack on a non-nuclear state by a nuclear state signals to all non-nuclear powers that, to counter the same fate, they will need to procure their own nuclear stockpile. The other non-nuclear nations will push forward with their own nuclear programs. Because, within nuclear deterrence theory, the only way in which a nation can prevent being the target of a nuclear attack is through mutually assured destruction.
The escalating rhetoric of President Trump and President Putin has worked to undermine deterrence theory, but if they continue on their current path of escalation through increasing their nuclear arsenals they might just get to test it.