India vs Pakistan: A military shootout
India's nuclear doctrine
India has a declared nuclear no-first-use policy and is in the process of developing a nuclear doctrine based on "credible minimum deterrence".
In August 1999, the Indian government released a draft of the doctrine which asserts that nuclear weapons are solely for deterrence and that India will pursue a policy of "retaliation only". The document also maintains that India "will not be the first to initiate a nuclear first strike, but will respond with punitive retaliation should deterrence fail" and that decisions to authorise the use of nuclear weapons would be made by the Prime Minister or his 'designated successor(s)'.
Pakistan's nuclear doctrine
Pakistan's motive for pursuing a nuclear weapons development program is never to allow another invasion of Pakistan. President Muhammad Zia-ul-Haq summed it up in 1987 when he stated to Indian Prime Minister Rajiv Gandhi: "If your forces cross our borders by an inch, we are going to annihilate your cities".
Pakistan has not signed the Non-Proliferation Treaty (NPT) or the Comprehensive Test Ban Treaty (CTBT).
According to the U.S. Defense Department report cited above, "Pakistan remains steadfast in its refusal to sign the NPT, stating that it would do so only after India joined the Treaty.