During the Cold War, when the United States faced the threat of a nuclear attack, U.S. administrations made clear that any strike would prompt an all-out retaliation.

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Syria said the strike targeted a military research facility and vowed retaliation, but has so far refrained from any response.

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The convention bans such systems under the belief that a country would not launch a nuclear strike if it were unable to protect itself against retaliation.

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