The campaign to liberate Mosul from the Islamic State (IS) stands at a critical juncture, as Iraqi forces reportedly near the outskirts of the terrorist organization’s stronghold.

Even as the battle approaches its climax, however, the Iranian regime seeks to exploit the city’s post-IS vacuum by creating a land corridor from Iran to Syria and Lebanon, thereby enabling Tehran to expand its influence in the region.

In the coming weeks, the United States must take steps to ensure that the Iraqi people, rather than Iran, will be the operation’s primary beneficiary.

  • Over the weekend, Iran-backed Shiite militias opened a new front to Mosul’s west, as Iraqi army and Kurdish Peshmerga forces target the city from the south and northeast. The Shiite militias, known as the Popular Mobilization Forces (PMF), aim to secure Iraq’s western border, thereby blocking the flow of fighters and supplies between Mosul and Raqqa, the de facto capital of IS. Although the PMF’s action may help degrade IS following the fall of Mosul, the Iranian-backed group will leave Tehran in control of smuggling routes through Iraq.
  • To be sure, the PMF’s overt role in the battle for Mosul seems smaller than its role in earlier operations against IS-controlled territory, giving Iran plausible cover to deny its larger ambitions in the country. Ali Akbar Velayati, an advisor to Iran’s supreme leader, Ayatollah Ali Khamenei, claimed earlier this month that Tehran “is not directly involved” in Mosul. An Iranian government spokesman, Mohammad Baqer Nobakht declared that Iran retains “no ground forces in Mosul although it has assisted the country from the very beginning of the conflict through offering advisory help” to defeat IS.
  • In fact, since the rise of IS in 2014, the PMF has fueled sectarian tensions by inflicting sustained human rights abuses against Sunni populations. In this context, the predominance of Iraqi army and Kurdish Peshmerga forces in the Mosul offensive appears to reflect Baghdad’s recognition that Iran-backed militias threaten prospects for Sunni-Shiite reconciliation in a post-IS Iraq. Still, the PMF’s reduced involvement hardly suggests that Tehran lacks a vested interest in Mosul. Rather, Iran and its proxies remain poised to capitalize on the U.S.-backed coalition’s likely victory over IS by increasing its control of Iraqi territory.

The prospect that the fall of Mosul would strengthen Tehran’s strategic position has contributed to longstanding tensions between Iran and Turkey. As Zalmay Khalilzad, a former U.S. ambassador to Afghanistan, Iraq and the United Nations, noted following a recent visit to Turkey and Kurdistan, Ankara fears that Iranian control of the territory surrounding Mosul “would allow Iran to project power” on behalf of the Assad regime, and “give Iran the ability to harass the Kurdish Regional Government in Iraq.” “The Turks believe,” Khalilzad added, “Iran is seeking a land corridor to the Mediterranean shores of Syria and Lebanon for which Mosul would present the shortest route from Iran — an outcome [Turkey] want[s] to block.”

These concerns constituted a key reason for Ankara’s recent push to join the military campaign for Mosul. The Iraqi prime minister, Haider al-Abadi, citing “Iraqi dignity,” rejected Ankara’s demand, but the PMF’s latest maneuvers west of Mosul may yet spur the Turkish president, Recep Tayyip Erdogan, to act unilaterally, thereby further complicating the Mosul campaign and risking a broader Turkish-Iraqi conflict. In this respect, Ankara has already demonstrated its willingness to defy Baghdad. On October 23, Ankara announced that Turkish troops in Bashiqa, a town east of Mosul, fired at IS positions in response to a request from Kurdish Peshmerga forces. Turkey had deployed the troops to Bashiqa late last year without Baghdad’s permission, triggering outrage in the Iraqi capital.

Ankara’s alarm at Tehran’s malign role in Iraq reflects wider Sunni Arab and Israeli anxieties regarding the rise of a “Shiite crescent” that would fill the void left by IS in Iraq and Syria. As the British-Israeli journalist Anshel Pfeffer notes, for the past 20 years, Iran has maintained two major arms smuggling routes. The first, which remains operational, entails aerial flights to Damascus International Airport followed by land shipments to Hezbollah forces in Syria and Lebanon. The second, now defunct, required naval shipments from Iran’s ports in the Persian Gulf to Sudan followed by further smuggling overland and then via ships from Egyptian or Libyan harbors. In early 2016, Sudan cut ties with Iran in response to an assault by Iranian protestors against the Saudi embassy in Tehran following Riyadh’s execution of a prominent Shiite cleric.

If Tehran’s plans for Iraq succeed, however, it would maintain a direct land route to Lebanon that would enable the dramatic intensification of its arms deliveries’ frequency and scale — particularly given the limited cargo space of Iranian airplanes and Israel’s record of targeting Hezbollah convoys by air. For this reason, after the defeat of IS in Mosul, President Obama — or, more likely, his successor — must take steps to ensure that Iran cannot benefit from the resulting vacuum. At a minimum, such an approach will require a greater U.S. military commitment to stabilize Iraq and reduce the influence of Iran and Sunni extremism. Only then can any diplomatic initiative to reconcile the country’s warring factions succeed.

By Senior Policy Analyst Tzvi Kahn from Foreign Policy Initiative