Afghanistan–Iran relations

Relations between Afghanistan and Iran were established in 1935 during King Zahir Shah's reign and the Shah of Iran Reza Shah Pahlavi, though ties between the two countries have existed for millennia. As a result, many Afghans speak Persian, as Dari (an eastern dialect of Persian) is one of the official languages of Afghanistan, and many in Afghanistan also celebrate Nowruz, the Persian New Year.

Quotes

 * Iran’s Qods Force provided training to the Taliban in Afghanistan on small unit tactics, small arms, explosives, and indirect fire weapons. Since at least 2006, Iran has arranged arms shipments to select Taliban members, including small arms and associated ammunition, rocket-propelled grenades, mortar rounds, 107mm rockets, and plastic explosives.
 * —U.S. State Department’s 2009 Country Reports on Terrorism. Thomas Joscelyn, “State Department: Iran Supports Taliban, Iraqi Militants,” Long War Journal, August 6, 2010; Kemp and Driver-Williams, “Killing Americans and Their Allies.” also quoted in (Complete Infidel's Guides) Robert Spencer - The Complete Infidel's Guide to Iran-Regnery Publishing (2016)