That's when U.S. and foreign intelligence first tracked a small number of senior al Qaeda terrorists as they moved from Afghanistan and Pakistan into Syria.
Khorasan soon imported additional operatives from wide-ranging terror cells in Chechnya, Iraq, Iran, Yemen and North Africa.
Khorasan found sanctuary with al Qaeda's Syria-based affiliate al-Nusra. And as Nusra battled to carve out operating space, Khorasan took advantage of the safe haven to begin plotting external attacks against Europe and the U.S.
Sources say Khorasan, with the help of al Qaeda bomb-makers, is working on developing concealable explosives that could be smuggled aboard airplanes. And Khorasan is actively recruiting jihadis with Western passports as potential operatives to conduct attacks in their home countries.
It was this threat that prompted the TSA in July to tighten security for U.S.-bound flights from foreign airports. Cell phones and laptops with dead batteries were banned for fear the devices could be used to hide bombs.
In carrying out this week's airstrikes, the Pentagon claimed it had disrupted "imminent attack plotting" by Khorasan. And officials say the group did have all the pieces in place to soon move to an execution phase.
But intelligence sources say no attack was on the immediate horizon. Khorasan had not yet selected targets or launched operatives.
The U.S. airstrikes did considerable damage. Pentagon officials said today the bombs and missiles hit every intended target. Khorasan's plotting has been disrupted. But, sources say there's no reason to think the threat posed by Khorasan has been eliminated.