One of my biggest fears is that a nuclear war could start by accident, or as the result of a miscalculation. Some national leader could push a threat too far, an exercise could be misinterpreted, things during a conventional war could get out of control, and cities could suddenly get incinerated.
It seems quite likely that Canada’s major cities are the targets of ex-Soviet missiles spread around Russian subs and silos. We may be the targets of Chinese bombs, as well.
Two important policy objectives seem to be (a) keeping additional countries from developing nuclear weapons (b) reducing the stockpile of weapons possessed by existing nuclear weapon states and (c) building systems that reduce the chances of accidents, including permissive action links to prevent unauthorized use of bombs and delays in hair-trigger systems.