The announced withdrawal of U.S. forces from Afghanistan will grant Iran one of its biggest wishes and lead to the departure of all foreign forces, which Tehran has long blamed for insecurity in the region.
Analysts say the pullout of U.S.-led NATO forces from Afghanistan could potentially give Iran more room to maneuver within its war-torn neighbor, with which its shares cultural and religious ties.
But if Afghanistan spirals into chaos -- as some Afghans fear -- then Iran could be faced with the problems created by a humanitarian and security spillover as it did during the Afghan civil war, when Tehran was faced with an influx of refugees and, later, a hostile Taliban government.
"I think for the Iranians, I'd say, 'Be careful what you wish for, you just might get it,'" says Colin Clarke, director of research and policy at the Soufan Group. "In other words, while Iran has been beating the drum for a U.S. withdrawal for years, there are potential second-order effects that Tehran might struggle with."
U.S. President Joe Biden on April 14 announced that the remaining 2,500 U.S. troops in Afghanistan will be leaving by September 11. NATO said it will follow Washington's timetable and pull its remaining 7,000 non-U.S. soldiers out of Afghanistan by the same date.
Andrew Watkins, a senior Afghanistan analyst with the International Crisis Group, says the departure of U.S. and NATO forces will certainly leave something of a power vacuum, giving Tehran more space to seek influence both with Afghan officials and other power brokers in the country, including the Taliban.
But he adds that "it is unclear how much Iran's essentially defensive, border-oriented interests in Afghanistan would expand, if at all."
"Throughout the U.S.-led intervention in Afghanistan, Iran has sought to gain influence among local actors and stymie U.S. interests, but via a low-risk, low-reward approach," says Watkins, who notes that "Iran generally exercises more restraint on its eastern border than it often has westward looking to the [Persian Gulf and the Levant]."
Fear Of A Vacuum
Speaking on April 16, Iranian Foreign Minister Mohammad Javad Zarif described the "responsible" departure of U.S. forces as a "positive move," saying the "presence of foreign forces has never contributed to peace and stability in our region and [their] removal will lead to at least less grounds for violence."
But Zarif also warned against a "vacuum" forming that the militant Taliban could try to fill. "That is a recipe for a new war in Afghanistan and we in the region cannot tolerate, with 3 million Afghan refugees in Iran, we cannot bear more burden," he said in on online discussion with Afghan and Indian officials. He added that Iran and other countries in the region need "a stable Afghanistan, a peaceful Afghanistan."
Analysts say that in the case of increased violence in Afghanistan, Tehran could work with regional allies to ensure stability, fortify its borders, as well as deploy its proxy forces, which have played a key role in promoting Iran's interests in the region.
Tamim Asey, executive chairman of the Institute of War and Peace Studies in Kabul, says Tehran's actions going forward will depend on its level of threat perception from Afghanistan, adding that Iran could work with regional powers that have similar interests in order to prevent the Taliban from returning to power.
"In fact, Iran could revive the axis of Iran, Russia, and India to support a second national resistance against the Taliban if Afghanistan plunges into a civil war," Asey, a former Afghan deputy defense minister, told RFE/RL.
The Daesh Threat
The Soufan Group's Clarke says Tehran could also secure its porous border with Afghanistan with more troops if the security situation worsens. "If a U.S. withdrawal leads to an immediate return to civil war in Afghanistan, as some have predicted, Iran is going to move quickly to fortify its border and ensure that spillover violence is mitigated," he told RFE/RL.
In his April 16 comments, Zarif warned about the presence in Afghanistan of the extremist Islamic State (IS) group, also known as Daesh, which has claimed responsibility for a number of deadly attacks.
"Now we see the role of Daesh; we don't know who's supporting Daesh in Afghanistan but of course we have some circumstantial evidence about the people behind the transfer of Daesh from Iraq and Syria to Afghanistan," Zarif said.
He added that "Daesh is a threat to Afghanistan, to Iran, to Pakistan, to everybody -- so we have a common threat."
Clarke says one byproduct of a U.S. withdrawal could be an uptick in IS plots and attacks targeting "Iran and or Iranian assets in Afghanistan."
"The Islamic State's Afghan branch has repeatedly attacked sectarian targets and, if it hopes to rebound from a string of recent setbacks, it'll likely resort to its playbook," he says.
In that case, Clarke suggests Tehran could deploy the Fatemiyoun Brigade, which has fought in Syria. The militia -- whose members are reportedly recruited and trained by the Islamic Revolutionary Guards Corps -- is comprised mainly of men from Afghanistan's Shi'ite minority. Between 2,500 to 3,500 Fatemiyoun fighters are believed to have returned to Afghanistan.
In a December 2020 interview with Tolo TV, Zarif suggested the Fatemiyoun fighters could help Kabul's fight against IS. "They are the best forces with a military background in the fight against Daesh. The Afghan government, if willing, can regroup them," Zarif said in remarks that were criticized.
Watkins believes all sides in Afghanistan are likely to oppose the deployment of the Fatemiyoun Brigade. "Both Taliban and the Afghan state, and many other stakeholders, would see them as foreign proxies and threats to their authority. Not to mention, the brigade is made up of Hazaras, an ethnic minority that widely feels under siege around the country, and in need of community defense [not aggressive expansion]," he says.
Biden has said Washington will ask other regional states to "do more" to support Afghanistan.