Since May, American forces in Syria have attacked a supply convoy of Iranian troops and Iran-backed militias and shot down two Iranian drones and one Syrian fighter jet. In each of these cases, Iran and its allies had first violated the U.S. zone of operations established by agreement with Russia; in two cases, aircraft directly attacked American troops. Tehran also fired ballistic missiles at Islamic State (IS) targets in the Euphrates River Valley, a move, Nader Uskowi writes, “signaling to all [Iran’s] opponents, including the United States and its allies, its intention to compete in the area after the Islamic State falls.” Thus, Uskowi argues, as IS is on the verge of crumbling, Washington must seek to thwart Iran’s plan to consolidate its influence throughout Syria:

Iran-led forces . . . will present arguably the greatest future threat to U.S. military personnel and interests in Syria. In the Iraq-Syria border region, Iran is executing a strategy centered on establishing a land bridge to Syria through Iraqi territory. Such a plan will inevitably cause direct conflict with U.S.-backed Sunni opposition forces. . . . [Their] big battles will thus be fought against the Shiite militias, led by Iranian special forces. . . .

The new battlespace in formerly IS-held territories . . . calls for a new U.S. policy, the chief component of which should be a strategy targeting Iran’s Qods Force and its Shiite militias. . . . Iranian strategy unmistakably focuses on defeating U.S.-supported opposition forces and pushing the United States out of Syria. Absent a new strategy that addresses Iran’s involvement in Syria, U.S. and allied forces could [do little more than] resort to self-defense tactics when under attack. In the process, such relative passivity could embolden Iran to raise the temperature in hopes of booting U.S. forces from the country. . . .

Iran-led forces are, with strong backing from Russia, already in control of Alawite-led western Syria. Their expansion into the Sunni-majority east and south could prolong the civil war and risk widening it further, . . . pitting major powers against each other. . . . Any attempt by Iran to extend the Sunni-Shiite conflict into those regions should be stopped in its tracks.

There is little doubt that if Hizballah had participated more intensively in Saturday’s attack, Israeli air defenses would have been pushed past their limits, and far more damage would have been done. Daniel Byman and Kenneth Pollack, trying to look at things from Tehran’s perspective, see this as an important sign of caution—but caution that shouldn’t be exaggerated:

Iran is well aware of the extent and capability of Israel’s air defenses. The scale of the strike was almost certainly designed to enable at least some of the attacking munitions to penetrate those defenses and cause some degree of damage. Their inability to do so was doubtless a disappointment to Tehran, but the Iranians can probably still console themselves that the attack was frightening for the Israeli people and alarming to their government. Iran probably hopes that it was unpleasant enough to give Israeli leaders pause the next time they consider an operation like the embassy strike.

Hizballah is Iran’s ace in the hole. With more than 150,000 rockets and missiles, the Lebanese militant group could overwhelm Israeli air defenses. . . . All of this reinforces the strategic assessment that Iran is not looking to escalate with Israel and is, in fact, working very hard to avoid escalation. . . . Still, Iran has crossed a Rubicon, although it may not recognize it. Iran had never struck Israel directly from its own territory before Saturday.

Byman and Pollack see here an important lesson for America:

What Saturday’s fireworks hopefully also illustrated is the danger of U.S. disengagement from the Middle East. . . . The latest round of violence shows why it is important for the United States to take the lead on pushing back on Iran and its proxies and bolstering U.S. allies.