The release of the Bin Laden library files shed new light on the links between Al Qaeda and Iran.
Iran harbored, trained and aided Al Qaeda in its campaign against America. Relations began to decline significantly when the Iraq War opened up a new front. Al Qaeda in Iran began aggressively targeting Shiites despite attempts by Osama bin Laden to head off Zarqawi's campaign. This led directly to ISIS.
The US invasion of Iraq, intentionally or unintentionally, created a serious breach in the Iran-Al Qaeda alliance. Not a fatal one. But a quite serious one.
This Atlantic article has been passed around quite a bit. It contains some interesting tidbits gathered from various sources, including interviews, and while it does the ritualistic Bush bashing and occasionally attempts to defend Iran, it does contain an interesting piece of information.
The next wave came early in the summer of 2002, when high-ranking al-Qaeda leaders arrived in Iran intending to stay and galvanize the outfit. They were marshaled by Abu Musab al-Zarqawi, the Jordanian thug who would form al-Qaeda in Iraq, the forerunner to ISIS.
That's quite significant because it gives us a first direct link between Iran and ISIS.
There have been various more current rumors about the relationship between the two. Especially in Syria. But this gives us a starting point.
The first to come was Saif al-Adel. A former colonel in the Egyptian Special Forces, he traveled under the pseudonym Ibrahim. He was accompanied by fellow Egyptian and al-Qaeda council member Abu Mohammed al-Masri—whose papers identified him as Daoud Shirizi—a former professional soccer player who was also wanted by the FBI for involvement in the 1998 embassy attacks. Joining them was Abu Musab al-Suri, one of the most important strategic voices in the movement. Immediately, a re-formed al-Qaeda military council planned its first attack from within Iran, according to Mahfouz, striking three residential compounds in Saudi Arabia, killing more than 35 people (including nine Americans) in 2003.
Those aren't the Khobar Towers Bombing, which more people are familiar with, but the Riyadh Compound bombings.