Few tears will be shed in many parts of the world for Maj. Gen. Qassim Suleimani, whose Quds Force of the Islamic Revolutionary Guards Corps ruthlessly spread Iranian influence and contributed to the deaths of thousands of Syrians, Iraqis and Iranians, as well as hundreds of American servicemen in Iraq, over the past decade and a half.

But revenge is not a strategy, and the killing of General Suleimani is a major — and incredibly risky — escalation with Iran, a pivotal country of some 80 million people that has been largely estranged from the United States for 40 years. It will cause more instability and the loss of more innocent lives. Any chances for American diplomacy with Iran are dead for the duration of the Trump presidency — if not longer. Instead of one nuclear proliferation crisis, with North Korea, there will most likely now be two, as the 2015 Iran nuclear deal completely collapses. The Sunni fundamentalists who killed Americans in their homeland — something Iran has not done so far — will rejoice. Russia and China will be happy to see the United States mired in the Middle East for the foreseeable future.

It is important to remember who began this spiral. In May 2018, President Trump unilaterally withdrew from the nuclear agreement negotiated by his predecessor at a time when Iran was in full compliance with it. When he did so, the Quds Force and its associated militias in Iraq were fighting the Islamic State in indirect coordination with the American military. The Persian Gulf was quiet.

For a year after the American withdrawal from the nuclear deal, the status quo prevailed. Then in April 2019, Secretary of State Mike Pompeo announced what amounted to an embargo on the export of Iranian oil. Shortly afterward, Iran moved from “strategic patience” to resistance and retaliation: first against oil tankers, then against an American drone and in September against Saudi oil facilities. In Iraq, Iran-backed militias started lobbing rockets into the Green Zone and other locations where Americans are based. On Dec. 27, rockets killed an American contractor in Kirkuk, and the United States retaliated with strikes that killed two dozen militia members in Iraq and Syria. Iran-backed militias responded with an attempt to break into the American embassy in Baghdad on New Year’s Eve.