So much for the taunt from Iran’s “supreme leader,” Ayatollah Khamenei, that America “cannot do a damn thing” about Iran’s attack on our embassy in Baghdad. It took President Trump but a day after that jibe to wheel on the Iranians. He launched a drone attack that found and killed the commander of Iran’s Revolutionary Guard Corps, General Qassim Soleimani. It is likely to mark a turning point in the not-so-quasi war that Iran has been levying against us — and, among others, Israel.

This is not a situation in which responsibility is being debated on murky evidence. The Pentagon itself put out a straightforward statement saying that our military had acted “at the direction of the president.” It characterized the attack as a “decisive defensive action to protect U.S. personnel.” The Pentagon pointed out that Soleimani’s Islamic Revolutionary Guard Corps-Quds Force is an American-designated foreign terrorist organization.

“General Soleimani and his Quds Force,” the Pentagon noted, “were responsible for the deaths of hundreds of American and coalition service members and the wounding of thousands more. He had orchestrated attacks on coalition bases in Iraq over the last several months — including the attack on December 27th — culminating in the death and wounding of additional American and Iraqi personnel.” It was Soleimani also approved the attacks this week on our embassy in Baghdad.

Our “counterstrike” today was, the Pentagon said, “aimed at deterring future Iranian attack plans.” That aim was underscored by reports that among those slain in the strike were Abu Mahdi al-Muhandis, who commanded an Iranian backed terrorist militia called Kata’ib Hezbollah. America, the Pentagon said, would “continue to take all necessary action to protect our people and our interests.” Our attack was, among other things, a product of remarkable intelligence.

As astounding as the attack may be on the order of battle in the Middle East, it may be even more of a game-changer politically, including here at home. The attack, after all, lands in the middle of not only an American presidential impeachment but also a presidential election. So far, the Democrats have barely focused on foreign policy, except as part of their efforts to portray Mr. Trump as improperly trying to dragoon the Ukrainians into investigating Vice President Biden.

Yet the smell of cordite was still over the Baghdad Airport when the Democrats started caviling. The attack on Soleimani, Vice President Biden complained, was a “hugely escalatory move in an already dangerous region.” Senator Warren called the attack “reckless” and said that “our priority must be to avoid another costly war.” Senator Sanders said that Mr. Trump had “promised to end endless wars” and asserted that this “puts us on the path to another one.”

We’ll see what Iran wants. Our own view is that Mr. Trump has shown as much forbearance as anyone could expect of a responsible leader in the face of repeated Iranian aggression, over a long period of time, against us, the Saudis, and Israel. The President even reached out to the Iranian camarilla diplomatically, which was more than they deserved. Mr. Trump clearly grasped that any failure to respond to Iranian aggression would have carried its own risks.

This is a moment to remember that Iran’s regime holds power by main force. It has been facing riots and protests from millions of its own people. Is it too much for at least one of the Democrats to stop the politicking at the water’s edge and suggest that all Americans stand together in the face of what Iran is doing? If it turns out that Iran has precipitated a wider war, what will the Democrats do to help America win it?