When the United States killed Qassim Soleimani at the Baghdad airport in the early hours of January 3, the head of Iran’s Islamic Revolutionary Guard Corps (IRGC) was not the only target. With Soleimani was a handful of other Iranian brass as well as Abu Mahdi al-Muhandis, the leader of the Iraqi Shiite militia known as Kata’ib Hezbollah. Only days before, that group had fired on a base in Kirkuk and killed an American contractor. The group was also involved in the siege of the U.S. Embassy in Baghdad just days later.

Upending two decades of established U.S. foreign policy, Donald Trump cared little whether the perpetrators of the embassy attack and the missile strike in Kirkuk came from Iran or were surrogates of Iran based in Iraq. Iran was responsible, and Iran paid. In one stroke, Trump eliminated the Iranian figure who had been spearheading the bloody proxy war against America, Israel, and a number of Gulf Arab states dating back to the late 1990s.

Soleimani’s killing was, without question, the most consequential act of Trump’s presidency. It didn’t just punish Iran for the action of its proxies. After decades of the U.S. letting the Islamic Republic get away with murder, the Trump administration made it clear that America would no longer allow the regime to hide behind its militias.

In 2008, a former CIA analyst named John Brennan wrote an article for Annals of the American Academy of Political and Social Science in which he laid out what he thought was a logical case for not responding to Iran’s violent proxies in the Middle East. “While Iranian support to these client groups undoubtedly strengthens their ability to carry out terrorist attacks, it is unclear what role Iranian officials play, if any, in the operational decisions made by these groups,” Brennan wrote. “Moreover, while many of these groups’ activities are labeled as ‘terrorism,’ most of the attacks carried out by Iranian Shia proxies are paramilitary in nature and are directed against combatant targets, either Israeli soldiers along the Lebanese border or coalition forces in Iraq.”

Brennan, who served as director of the CIA under Barack Obama, was not alone. He was one of many intelligence and military officials who viewed with calm dispassion the Islamic Republic’s use of proxies to attack Americans or American interests. As a result, Soleimani went unchallenged during his tenure as the leader of Iran’s military elite from 1998 to 2020.

Soleimani’s most effective and deadliest aggressions against the United States are memorialized in the U.S. Army’s comprehensive two-volume study The U.S. Army in the Iraq War. After the end of the first phase of the 2003 Iraq War, Soleimani’s IRGC infiltrated the neighboring country, assassinated former leaders of the Saddam Hussein regime, and established safe houses for future operations. IRGC teams then deployed to organize, train, and equip Iran-backed militias. American personnel were increasingly targeted and killed by the deadly bombs known as explosively formed projectiles (EFPs). The Army report concluded that the “Qods Force and its Iraqi surrogates were the primary instruments employed by the Iranian regime to wage a proxy war against the United States at minimal cost.”

As an author of the study later summarized: “When evidence was becoming clearer that Iran was behind a deliberate and systematic series of attacks on Americans, the U.S. reviewed possible responses. The U.S. decided against a more aggressive response primarily out of fear of Iranian escalation.” In fact, when the Israelis actually had Soleimani in their crosshairs in 2008, the Bush administration asked them to stand down. All in all, the Pentagon assesses that at least 603 U.S. deaths in Iraq “were the result of Iran-backed militants.”

Upon ascending to office in 2009, Barack Obama almost immediately set into motion his plans for withdrawing a majority of U.S. forces from Iraq by 2011. Since the U.S. failed to solve the Iran-backed militia problem before leaving, our withdrawal precipitated a violent sectarian backlash against Iran’s Shiite proxies from Iraq’s Sunnis in the form of a new and brutal jihadist group: the Islamic State.

By 2014, the Obama administration quietly came to view Iran’s proxy groups as partners in the newly formed coalition to fight the Islamic State. When Iraq’s military proved feckless, it was the Shiite militias that pushed ISIS back, with Iraqi politicians in the capital of Baghdad cheering from the sidelines. Subcontracting the national defense in this way came at a price. The Iraqi state ceded its security to fighters loyal to Iran. Iranian officers embedded with the militias in Iraq. Soleimani himself appeared at some of their encampments, taking selfies and encouraging the fighters to continue the fight.

Among the more prominent groups to fill the security void in Iraq was Kata’ib Hezbollah—the very same group that would target an American base and the Baghdad embassy in December. The group’s leader, Abu Mahdi al-Muhandis, already had a reputation for having killed American soldiers during the Iraq war.

Another prominent Iran-backed militia that had fought Americans in Iraq before joining the fight against the Islamic State was Asa’ib Ahl al-Haq. The group claimed more than 6,000 attacks on U.S. troops, including many with EFPs. Its commander, Qais al-Khazali, was incarcerated by the U.S. military from 2007 to 2009, during which time he informed his interrogators that Iran planned to infiltrate Iraqi society at all levels.

The U.S. decision not to antagonize these Iran-aligned groups was based, in part, on their contribution to Iraqi security and their opposition to the Islamic State. U.S. policy was also calibrated to accommodate the Iranians as we pushed for a nuclear deal from 2013 to 2015. After the deal was reached, there was no debating the role of these militias or the danger they posed to Iraqi sovereignty. There was even a veiled attempt to identify these groups as independent, not subservient to Iran. This was fiction. Iraq had become an Iranian satrapy as a result of the 2011 U.S. withdrawal and the 2015 Joint Comprehensive Plan of Action. To add insult to injury, the militias were now funded, to one extent or another, by the $150 billion of frozen funds released by the Obama administration to Iran through the deal.

Under Soleimani’s guidance, Iran’s militias also operated well beyond Iraq. In Syria, the Iraqi Harakat Hezbollah al-Nujaba, the Fatemiyoun division of Afghan Shiite irregulars, the Zaynabiyoun brigade of Pakistani Shiite fighters, and others have slaughtered untold thousands of Sunnis. Their goal was to defend the Assad regime and, by default, the Islamic Republic’s interests in Syria. While the Obama administration slapped some militias with terrorism designations, it chose not to escalate beyond that. Once again, the American president feared jeopardizing the nuclear deal. The Trump administration did no better. As these groups were part of the effort to defeat ISIS, Trump looked the other way.

The United States has shown similar ambivalence toward Iran’s proxy in Yemen. The Houthi militia, also known as Ansar Allah, for years identified itself as an independent group of disaffected Shiite Muslims that had nothing to do with Soleimani’s project. This was an argument often parroted in prominent publications such as Foreign Policy, not to mention the halls of the U.S. Congress. This false narrative ultimately doomed the efforts of Saudi Arabia and the United Arab Emirates in their ill-fated war to purge the Iranians from Yemen. (Admittedly, errant air strikes that reportedly killed thousands of civilians didn’t help either.) But over time, the operational and financial ties between the Houthis and the IRGC have become increasingly clear. This was underscored just days after the Soleimani killing, when an IRGC officer was killed while working with the Houthis in Yemen.

The Islamic Republic’s proxy strategy is easy to understand. Local militias enable Iran to wage war against the United States or others with a measure of deniability. They are also crucial for the regime’s strategy to establish control of territory across the Middle East. Indeed, the Iranian strategy is hegemony. For the regime to conquer and control territory, it requires not just proxies but powerful ones.

The gold standard is the Lebanese Hezbollah. It was Iran’s first proxy. Today, it’s the regime’s predominant one. Incubated by the IRGC in Lebanon during the civil war there in 1975 and spurred on by the 1982 Israeli invasion, Hezbollah announced itself in the early 1980s with a series of attacks against American and French military installations. The jarring violence perpetrated by this group against America (241 Marines died in a 1983 attack) ultimately prompted President Ronald Reagan to redeploy U.S. troops from Lebanon.

Emboldened by this withdrawal, and urged on by Iran, the group turned its sights on Israel. A sustained guerrilla war ultimately prompted Israel to withdraw its forces from the security zone it had established in southern Lebanon in the year 2000. Twenty years later, Hezbollah continues to wage a low-intensity war against Israel without a casus belli.

Iran has armed, funded, and trained Hezbollah so that it could become one of the most formidable military forces in the Middle East. The group’s rocket arsenal is estimated at 150,000, including lethal precision munitions that may soon wreak havoc on the region. The group has fought in Syria, trained fighters in Iraq and Yemen, and carried out terrorist attacks at Iran’s behest worldwide, from Argentina to Bulgaria, again without paying a price.

With international attention focused on the group’s spectacular acts of violence, Iran has staged a slow-motion takeover of Lebanon. Hezbollah has wrested control of the country. Its military is stronger than the Lebanese Armed Forces. Hezbollah has been a part of every government coalition since 2005. It has slowly come to dominate state institutions. While the country’s population and politicians continue to assert Lebanon’s independence, that notion doesn’t hold up under serious scrutiny. But the longer the fiction of Lebanon’s independence can be maintained, the longer Iran will remain unimpeded to deploy its proxies to make or solidify territorial gains and engage in violence against its foes.

It was the denial of Iran’s pervasive influence that enabled Hezbollah to grow over the years. The refusal to acknowledge the regime’s control over other proxies has had a similar impact elsewhere. American denial of Iranian command and control allowed the regime to pursue a comparable strategy, from Iraq and Syria to Yemen and beyond.

Knowingly or not, with his targeted strike on Qassim Soleimani, Trump upended this dynamic. In holding the terror master responsible for attacks carried out by his Iraqi proxies, the U.S. president torched the thin firewall that long hindered American decisionmakers from holding Iran accountable. And in so doing, he appears to have pushed Iran’s proxies to dispense with the fiction as well.

On January 9, the commander of the IRGC’s aerospace command, Amir Hajizadeh, gave a press conference in front of the flags of the IRGC, Hezbollah, the Houthis from Yemen, and the Fatemiyoun and Zaynabiyoun militias. The message was clear: Iran commands all of them, and they all form an axis pitted against America in the aftermath of Soleimani’s killing.

Hassan Nasrallah, Hezbollah’s secretary general, effectively declared war on America after the targeted strike. He warned, “The response to Suleimani’s death is not a single operation but a long path that must remove U.S. military presence from the region.” Nasrallah added, “We are speaking about the start of a phase, about a new battle, about a new era in the region.” In a subsequent speech, he credited Soleimani for arming the organization. Nasrallah even spoke of Hezbollah’s new and lethal precision-guided munitions: “This is thanks to Iran, embodied in Soleimani.”

The Houthis slammed the killing of Soleimani as a war crime, vowing to respond to his death by expelling the “American occupier” from the region.

An official from Kata’ib Hezbollah released a statement calling for volunteers for suicide bombings against U.S. forces in Iraq and “the opening of the door of registration for the lovers of martyrdom, to conduct martyrdom operations against the foreign Crusader forces.”

One by one, Iran’s proxies are signaling that the death of Soleimani was a blow to their leadership. In so doing, they are acknowledging the command-and-control structure that Americans refused to concede for years: The militias are indistinguishable from the IRGC.

Trump is still unsure if he wants to leave Iraq. If he does, he’ll validate Soleimani’s strategy and breathe new life into his shadow armies. If he denies Iran that territory and holds the regime accountable for the actions of its proxies, he will have done something that no other president has done since the rise of the Islamic Republic in 1979. He’ll have changed the rules of the game.