I doubt the marines and sailors will be released anytime soon. Remember they held American embassy staff for 444 days. They have scored major status points in the Muslim world by showing they are "the strong horse" and the decadent, infidel Brits/US are "the weak horse". Iran will milk it all they can.

The capture of fifteen captives cannot be allowed to dictate foreign policy. To let the situation drag out without 100-fold retaliation is the same big mistake sniveling Jimmuh Carter made in 1979. It served to encourage the Iranians to launch their 28 year (and counting) war against us infidels.
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"The Americans will always do the right thing... After they've exhausted all the alternatives."

- Winston Churchill