The missiles used for interception aren't tipped with nuclear warheads. Therefor if the intention is strictly defensive, increased production of nuclear warheads aren't necessary.
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I believe Trumps intention is to puff his chest and "match" aggression with Putin. This action is really handy in a "who's gonna nuke who" pissing contest. except these pissing matches have to stop at words because the minute one launches, the risk is high, they will all launch.
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I don't want the last words I read on the internet be "I told you so" from Roy Anthony.