Ever since the development of nuclear weapons their employment has been a major concern of military planners. Fortunately, we have had no practical experience with their use. However, in the event of war in Western Europe a decision determining the threshold for their employment would be critical If not decisive.
Norton, Augustus R.
"NATO and Metaphors: The Nuclear Threshold,"
Naval War College Review: Vol. 30
, Article 5.
Available at: http://digital-commons.usnwc.edu/nwc-review/vol30/iss4/5