virtually all "high-alert nuclear weapons" are possessed by the u.s. and russia. both nations use automated command and control systems in conjunction with their early warning radar and/or satellites to facilitate the rapid launch of their land-based intercontinental ballistic missiles (icbms) and some submarine-launched ballistic missiles (slbms). fear of a "disarming" nuclear first-strike that would destroy their command and control systems and nuclear forces led both nations to develop "launch-on-warning" capability, which requires high-alert nuclear weapons able to launch on a 30-minute (or less) tactical warning, the nominal flight time of icbms traveling between the u.s. and russia.