Testing the Firebreak: Experimental Evidence on Low-Yield Nuclear Weapons and Deterrence in India and Pakistan

A cross-national shift toward lower-yield nuclear weapons has generated renewed interest in the integrity of the firebreak: the conceptual barrier between conventional and nuclear warfare. We theorize that low-yield nuclear weapons alter nuclear nonuse mechanisms. They threaten to breach the firebreak by offering a more credible, but less costly, deterrent and undercut norms grounded in nuclear weapons’ effects. To test the integrity of the firebreak, we conduct simultaneous survey experiments investigating how Pakistani and Indian citizens consider low-yield nuclear weapons use in an escalating crisis. We find a low-yield nuclear weapons threat to be credible, but not necessarily stabilizing. Both publics in this rivalry exhibit substantial willingness not only to issue a nuclear response to a low-yield nuclear strike, but also to introduce nuclear weapons into conflict. However, neither universally seeks retribution. Vivid information about nuclear effects moderates retaliation preferences among citizens who strongly favor their co-nationals.