David M. Allison argues that in ascending order of predictive power, warnings of an imminent nuclear strike would come from Russian whistleblowers, the U.S. intelligence community, and Putin himself.

For months, evidence has accumulated that North Korea may be preparing its seventh nuclear explosive test. Continuous warnings by analysts and the media about this possibility are a sobering reminder that Pyongyang's continued pursuit of a larger nuclear arsenal remains a challenge for the Non-Proliferation Treaty and the nonproliferation regime. This continues to be the case even as the public and leaders around the world have largely shifted their attention to the nuclear dimensions of the war in Ukraine.

How robust is public support for extended nuclear deterrence in patron and client states? Recent studies have improved scholarly understanding of US public opinion about nuclear weapon use against non-nuclear adversaries. Yet, there is limited knowledge of public attitudes regarding retaliation for nuclear strikes against US allies. We develop a theoretical typology of nuclear crises and investigate this phenomenon with a novel survey experiment (n = 6,623). Americans, Japanese, and South Koreans viewed realistic emergency alert messages about a most-likely case for nuclear retaliation: a North Korean missile attack on a US ally protected by the nuclear umbrella. Support for nuclear retaliation is low in all three countries, with important cross-national differences. Favorability increases with North Korean nuclear first-use, but it remains limited nonetheless. Surprisingly, US “tripwire” troop casualties do not increase Americans’ demands for nuclear retaliation. These findings have important implications for the study of nuclear crises and practice of extended deterrence.

David M. Allison and Stephen Herzog respond to Brendan Rittenhouse Green and Austin Long’s winter 2019/20 article, “Conceal or Reveal? Managing Clandestine Military Capabilities in Peacetime Competition.”

The administration of President Donald J. Trump has consistently used fear of China to undermine nearly five decades of bipartisan consensus on US–Russian nuclear arms control. The negative consequences of these actions may last far beyond the Trump presidency. If generations of agreement between Democrats and Republicans on bilateral nuclear treaties with Russia erode, it will pose a significant setback to US national security and global stability. Future leaders may ultimately need to consider new approaches to nuclear risk reduction that preserve the benefits of the arms control regime.

Damir Kovačević, Afrimadona, and Martin Claar's (KAC) statistical adjudication between the potential role of norms versus strategic deterrence in preventing interstate chemical-weapons use is a welcome contribution (Vol. 26, Nos. 3–4, pp. 251–66). The authors conclude that a powerful non-use norm is the most convincing explanation for downtrending chemical warfare. However, closer examination by  David M. Allison and Stephen Herzog in this response to the original article reveals several analytical issues, including inaccurate presentation of data and alternative explanations, that may undermine their results.

Miscalculation is unlikely when open conflict would come with high costs for both countries, costs that neither their leaders nor their publics are willing to accept.