One of the most useful maxims is to beware of the pitfalls of conventional wisdom. It is said that Iran and Al-Qaeda could not have any relationship because of the deeply entrenched Sunni/Shia difference between them. Perhaps, this divide does exist but there has been an operational relationship between the two sides, which has spanned for decades. This relationship began in early 1990’s in Sudan, which developed further when Al-Qaeda was in Afghanistan and continued even after the September 11 attacks. In July 2011, the United States formally accused Iran of having direct ties with Al Qaeda which resulted in the September 11 attacks.
The terrorist lynchpin
If one looks at the conventional wisdom that discounts the possibility of Sunni-Shia relationship, then please ask why has there never been an attack inside Iran from foreign Sunni terrorist groups?Faisal Al-Shammeri