The Afghan provinces of Herat, Farah, and Nimruz border Iran.
Iran and Afghanistan share several religious, linguistic, and ethnic groups that create cultural overlaps between the two countries.
But when a US-led coalition invaded Afghanistan in 2001 to overthrow the Taliban, Iran was not disappointed.
Iran played a key role in Afghanistan’s state-formation and reconstruction process in the immediate aftermath of the Taliban’s ouster.
Iran, along with Russia, provided arms and funding to the Northern Alliance throughout the civil war, while Pakistan and Saudi Arabia supported the Taliban.
Iran has a population of 66.4 million and it is one of the world’s only Shia-majority states, with Shia Muslims comprising 89 percent of the population or 58.6 million of people.
Iran also has a Sunni Muslim minority, which accounts for nine percent of the population or 5.9 million people.
Thus, Tehran supported the formation of an anti-Taliban coalition composed of mostly Tajik, Uzbek, and Hazara factions—including Hezb-e Wahdat.
This United Islamic Front for the Salvation of Afghanistan, also known as the Northern Alliance, was led by deposed ethnic Tajik President Burhanuddin Rabbani and his military commander Ahmad Shah Massoud.
While the Iranian leaders welcomed the fall of the Taliban, they also saw the presence of American troops in neighboring Afghanistan as a national security threat.