The common interest of the US and the USSR, in avoiding a nuclear war, has been expressed in a number of preventive measures. As a consequence, the risk of nuclear war by mistake is considered to be very low under normal conditions. However, if “crisis stability” decreases, a war by mistake could be started, through regeneration, even by incidental circumstances, especially in a situation of high political tensions. The authors propose a cybernetic approach which may contribute to the understanding of the risk of nuclear war by mistake, and to the evaluation of proposals aimed at reducing that risk. Some characteristics of the command and control system for the nuclear forces, as well as recent developments, are briefly described. Present threats to crisis stability are discussed for a simple one nation model, and in relation to a model of two nations. Preventive measures are proposed. Also, some other Swedish technological contributions, to International disarmament and conflict resolution, are briefly described. The emphasis is on the verification of arms control agreements.