Properly, Iran should be told that they must return the captives by (deadline- short) or we bomb the hell out of Iran the day after the deadline. Then, if the captives are not returned, we bomb the hell out of Iran. If the captives are returned we thank Iran profusely and praise Iran for its Cooperation, wait 2 days and bomb the hell out of Iran.
Taking out its govt, the mullahs, and a huge chunk of its military and the major known nuke sites without widespread civilian damage would probably be more prudent.