Pakistan's nuclear policy was significantly affected by the 1965 war with India. The 1971 war and India's nuclear program played a role in Pakistan's decision to go nuclear. India and Pakistan both decided not to participate in the NPT. Pakistan's nuclear policy became fixated on India because India refused to join the NPT and remain opened to nuclear weapons. Impetus by Indian actions spurred Pakistan's nuclear research. After nuclear weapons construction was started by President Zulfikar Ali Bhutto's command, the chair of Pakistan Atomic Energy Commission Usmani quit in objection. The 1999 war between Pakistan and India occurred after both acquired nuclear weapons. It is believed by some that nuclear weapons are the reason a big war has not broken out in the subcontinent. India and Pakistan still have a risk of nuclear conflict on the issue of war over Kashmir. Nuclear capability deliverable by sea were claimed by Pakistan in 2012. The aim was to achieve a "minimum credible deterrence". Pakistan's nuclear program culminated in the tests at Chagai. One of the aims of Pakistan's programs is fending off potential annexation and maintaining independence.