(Bloomberg Opinion) — For 40 years American presidents have pondered a fundamental question about Iran, best summed up by Henry Kissinger: Is it a country or a cause? On Thursday evening, Donald Trump gave his answer: Iran is a cause, a terrorist cause, and it will be treated as such.That could be the lasting implication of the drone strike Trump ordered that killed Iran’s indispensable General Qassem Soleimani. Since Jimmy Carter, U.S. presidents have sanctioned Iran and its leaders for sponsoring terrorist groups responsible for mayhem and murder worldwide. Until Thursday, however, those leaders have been spared the grisly fate of Osama bin Laden or Abu-Bakr al-Baghdadi.Nation-states are generally expected to cooperate against terrorists, but with Soleimani’s leadership Iran has been a major facilitator of terror. Starting in 2003, he built up a network of proxies throughout the Middle East that tipped the balance of power in Iran’s favor. Under his command, Shiite militias in Iraq injured or killed thousands of U.S. troops with powerful roadside bombs. He orchestrated the arming and training of Yemen’s Houthi rebellion. He planned the intervention in Syria that saved Bashar al Assad’s brutal war machine. He helped plan the Iraqi government’s crackdown against anti-Iranian protesters.And yet Soleimani saw himself as untouchable. He did not take the precautions of a marked man, cloaking his movements and hiding his location. In fact, he would often post selfies from various fronts in Iran’s regional war, taunting his adversaries.In some ways, this drone strike is surprising. In June, Trump called off at the last minute a strike on Iranian positions after it shot down an unmanned U.S. drone over the Persian Gulf. Over the summer and into the fall, Trump escalated sanctions against Iran’s regime, but also tried to restart negotiations with its political leaders. He has railed against the “endless wars” waged by his predecessors and sought to withdraw U.S. forces from Syria.Iran has responded to this economic pressure with military escalations. In September, the U.S. accused Iran of striking a major Saudi oil processing facility. This followed a series of Iranian attacks on oil tankers in the Persian Gulf. In October, Iranian-backed Shiite militias began hitting U.S. positions in Iraq. Those attacks have become bolder in recent months, culminating in an attack last week in Kirkuk that killed a U.S. contractor and wounded several U.S. servicemen.That crossed a red line for Trump. He has warned the Iranian regime since last spring that the U.S. would respond in kind to any attack that killed a U.S. citizen. The U.S. responded this week by bombing Kataib Hezbollah bases in western Iraq and Syria. Then Iranian-led militias stormed the U.S. embassy in Baghdad on Wednesday, setting fires and essentially holding diplomats hostage for 24 hours before retreating. Secretary of Defense Mark Esper issued a prescient warning after the siege. “If we get word of attacks,” he said, “we will take preemptive action as well to protect American forces, to protect American lives.”The consequence is that the man who orchestrated terror on behalf of Iran has met the same fate as the terrorists he oversaw. This counts as a significant escalation; Iran’s supreme leader has already vowed revenge. Hezbollah leader Hassan Nasrallah has urged Shiite militias in Iraq not to let Soleimani’s death go to waste.And Iran has many options for retaliation. Its militias have enough rockets to turn the the U.S. embassy in Baghdad into rubble. Its proxies are capable of kidnappings, suicide bombs and other mayhem against softer American targets in Europe. Hezbollah, a Lebanese militia and political party created by Iran in the 1980s, controls some networks inside the U.S.     That’s not to say the U.S. attack was unjustified. Soleimani was “actively developing plans to attack American diplomats and service members in Iraq and throughout the region,” the Pentagon said in a statement Thursday. “This strike was aimed at deterring future Iranian attack plans.”So it’s misleading to say that the killing of Soleimani is the opening of a new U.S. war against Iran. It’s more accurate to say that it opens a new chapter in an ongoing war. Until this week, that war has been waged through economic sanctions against Iran’s regime and precision strikes against its proxies. Now Trump has erased the distinction between Iran and its proxies.That’s a blow not just to Iran’s network of militias and terrorists. It’s also a blow to the regime’s campaign to bully the world into treating it like a normal country. Iran is a country run by terrorists, and Trump is right to treat them as such.To contact the author of this story: Eli Lake at [email protected] contact the editor responsible for this story: Michael Newman at [email protected] column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.Eli Lake is a Bloomberg Opinion columnist covering national security and foreign policy. He was the senior national security correspondent for the Daily Beast and covered national security and intelligence for the Washington Times, the New York Sun and UPI.For more articles like this, please visit us at bloomberg.com/opinion©2020 Bloomberg L.P.