Is America at war with Iran? We ask because when President Trump spoke to the nation after our aircraft were out of Iran, he pointedly refrained from saying we are at war. Vice President Vance went further. “We’re not at war with Iran,” he declared. “We’re at war with Iran’s nuclear program.” Whether Iran buys that argument is unclear, though it is attacking our bases. The question of whether we’re at war, though, is clearly something to mark.

Our own view is that America is not at war with Iran — but if we are at war, the conflict started a long time ago. One could trace the origin of the hostilities to the Iranian Revolution of 1979, when Islamic militants captured our embassy at Tehran and took hostage more than 50 Americans. That was a national humiliation for America, undermining our global leadership role — and helping to propel Ronald Reagan into the presidency. 

Since then one could view the entirety of Iranian-American relations as a kind of uneasy truce punctuated by periodic intensification. Feature, say, the attack by us in 2020 that killed Qasem Soleimani, to which Iran responded with missile strikes on American bases in Iraq. Mr. Trump’s strikes on Iran’s nuclear facilities may mark an escalation in this conflict. Yet the question of whether it is a war is more than merely semantic.

After all, was it a war when past presidents opted, say, to deploy America’s military forces in, say, Libya, Bosnia, or Somalia? Stanford Law’s Michael McConnell points out that those engagements cost billions of dollars and thousands of lives. Mr. McConnell notes that President Obama’s Libyan engagement “was in no sense defensive, nor was there anything sudden about it.” Did President Clinton make war by bombing the former Yugoslavia?

The importance of clarifying this distinction comes amid grumbling from Democrats — and at least some Republicans — over whether Mr. Trump’s actions, in his capacity as commander in chief, to keep Americans safe amount to a breach of the Constitution. Senator Kaine, a leading opponent of the president’s freedom of action in military affairs, calls Mr. Trump’s move against Iran “an offensive war of choice.”

“I hope members of the Senate and the House will take their Article I responsibilities seriously,” Mr. Kaine scolds. Such seriousness wouldn’t necessarily imply the need to curb Mr. Trump’s authority to superintend America’s military engagement vis-à-vis Iran, though. Mr. Kaine’s pettifoggery appears to be concerned more with constraining America’s forces than with achieving victory in our unfolding conflict with Iran.

The tumult on Capitol Hill over the president’s war powers is a reminder that Congress has the power to “declare” war — but that is not the same as making war. Plus, too, America can be at war if someone else attacks us. That, in effect, is what happened at Pearl Harbor in 1941 when the Empire of Japan attacked America without first declaring war. America’s ensuing declaration of war was careful to mark this point.

At President Roosevelt’s request, Congress resolved “that the state of war between” America and Japan “which has thus been thrust upon the United States is hereby formally declared.” In declaring war, the Congress, flexing its constitutional muscles, also “authorized and directed” the president “to employ the entire naval and military forces” and “the resources of the Government” to wage the war and “to bring the conflict to a successful termination.”

The legislators in 1941 noted, too, that to achieve the aim of victory, “all of the resources of the country are hereby pledged by the Congress of the United States.” Contrast that stalwart framing of the wartime responsibilities of the president and the Congress in the war against Japan with the authorizations to use military force that the Congress deployed in America’s conflicts with, say, Vietnam, Iraq, and Afghanistan.

It’s no accident, as these columns noted when Mr. Kaine was trying to thwart Mr. Trump from a move against Iran, that America’s declared war against Japan ended in victory, while the more recent conflicts “fizzled out in either disgrace or surrender.” That underscores the need to get it right today as the president and Congress, in their constitutional capacities, determine whether America’s conflict with Iran amounts to a war.