national technical means of verification (ntm) are monitoring techniques, such as satellite photography, used to verify adherence to international treaties. the phrase first appeared, but was not detailed, in the strategic arms limitation treaty (salt) between the us and ussr. at first, the phrase reflected a concern that the "soviet union could be particularly disturbed by public recognition of this capability [satellite photography]...which it has veiled.". in modern usage, the term covers a variety of monitoring technologies, including others used at the time of salt i.