Tell Congress and the President that you do not support military action against Iran, that you do not support preemptive war against Iran.
Why is this important?
As an American citizen I don't feel that we can afford another preemptive war such as the one we initiated in Iraq. We cannot afford it. The military option with regard to Iran should be OFF the table, NOT on the table. Moreover, explicitly taking the military option off the table would give Iran much less of an excuse to behave in destructive ways. Iran's behavior is the result of past western intrusion into its affairs, and the existence of the military option that is on the table.
