Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain
the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in
Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles
Nuclear tensions are escalating between south Asia’s two superpowers — India and Pakistan — following the Indian defence minister's announcement earlier this month that India may revoke its current commitment to only use nuclear weapons in retaliation for a nuclear attack, known as ‘no first use’.