In 2001 , the invasion of Afghanistan and the removal of the Taliban in the wake of the September 11 attacks benefited Iran , which had previously been on the brink of war with the group . The regime change removed Iran 's primary threat along its eastern borders , and the removal of Saddam Hussein two years later further bolstered its position , allowing it to refocus its efforts on other areas , especially Syria and Yemen . In the ensuing years , Iran sought to expand its influence over Afghanistan . It provided limited support to the Taliban as a potential means of increasing leverage with the Afghan central government and creating a deterrent to conflict with the United States , although the support waned amid growing backlash in Afghanistan against perceived Iranian interference . Iran has also sought to expand soft influence by building pro-Iranian schools , mosques , and media centers , and by maintaining close ties with Afghanistan 's Tajik and Hazara populations
September 11 attacks
September 11 attacks
Iran–Saudi Arabia proxy conflict