Iran is a nation-state. For us, as a nation-state, to go to war against Iran requires a declaration of war, which is the exclusive province of Congress. This is different from military hostilities against non-state militias who are engaged in violence against allied nations. Just because Iran may provide assistance to these non-state militias, this is not grounds for an attack upon Iran as a nation-state. We provided assistance to the Contras who were engaged in violence against the new government of Nicaragua. We provided assistance to the Islamic fighters who were working to drive Russian troops out of Afghanistan (and who later became the Taliban). Did that give the Russians justification to kill one of our generals, or visiting Congressmen.? If Russia had declared war on us, we would have responded appropriately. But Russia wisely did not declare war on the U.S. We would be wise not to declare war on Iran. How could we invade and occupy Iran? How could we get Iran to stop fighting against us? The collective wisdom of Congress is greater than the impulsive undertakings of Donald Trump in the case of war against Iran.