No first use

A no first use (NFU) policy is a commitment by a nuclear power not to initiate the use of nuclear weapons. Such a pledge would allow for a unique state of affairs in which a given nuclear power can be engaged in a conflict of conventional weaponry while it formally forswears any of the strategic advantages of nuclear weapons, provided the enemy power does not possess or utilize any such weapons of their own. The concept is primarily invoked in reference to nuclear mutually assured destruction but has also been applied to chemical and biological warfare, as is the case of the official WMD policy of India.