Iran’s way of war is informed by the recognition that while it is a major regional power, it is no match for America militarily. According to the Global Firepower ranking, which the United States leads, Iran has the 14th-most-powerful military in the world, in between Brazil’s and Pakistan’s. The Iranians have a nuclear program but no nuclear weapons yet. They have a ballistic-missile program but no long-range missiles that can reach the United States. Iran has decent relations with Russia and China but no stalwart great-power allies; as one of the world’s most isolated countries, it does not have many allies at all. And while the Iranians have 523,000 active-duty forces and another 350,000 reserves, which is nothing to scoff at, their conventional military is hobbled by aging equipment, international sanctions, and restrictions on arms imports.

Tehran’s solution has been to engage with the United States asymmetrically, including influence operations and, more recently, cyber activities. At the forefront of this effort has been the country’s Islamic Revolutionary Guard Corps and especially its Quds Force unit, which Soleimani commanded. The IRGC has exploited internal conflicts and weak states in the Middle East, cultivating proxy forces—such as Shiite militias in Iraq, Bashar al-Assad’s regime in Syria, Houthi rebels in Yemen, and the militant group Hezbollah in Lebanon—that serve as a kind of alliance network to rival America’s regional alliances.

In a recent analysis, the International Institute for Strategic Studies noted that Iranian leaders have concluded that their most potent weapon is their “sovereign capability to conduct warfare in battlefields across the Middle East through third parties,” which “has encountered no effective international response but has consistently delivered Iran advantage without the cost or risk of direct confrontation with adversaries,” which could endanger the Iranian regime.

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Indeed, a list recently compiled by the Congressional Research Service of 20 Iran-related terrorist attacks or plots against the U.S. and its allies since the 1979 Islamic Revolution shows that nearly all were carried out by proxies such as Hezbollah, by the IRGC, or by Iranian intelligence. Be it the 1996 bombing of a U.S. military housing facility in Saudi Arabia or the deaths of hundreds of American troops at the hands of Shiite militias during the Iraq War, the details and extent of Iran’s involvement in harming the United States are often sketchy.

This pattern has continued with Iran’s reaction to Donald Trump’s decision in May 2018 to withdraw the United States from the 2015 nuclear deal and to reimpose sweeping sanctions on Tehran. After a year-long period of calculated restraint in Tehran came mysterious attacks on oil tankers in the Gulf of Oman and a shoot-down of an unmanned U.S. drone in June (the latter of which the Iranians uncharacteristically admitted to carrying out), a murky attack on Saudi oil facilities in September, and a rocket barrage by an Iran-backed Iraqi militia that killed an American contractor in December, leading to the latest surge in tensions.