Sadiq is actually Lambert.
Lambert miraculously survived Sam shooting him in the head in Double Agent, and went into hiding during the events of Conviction. First, how do we know Lambert survived? After Sam shoots him, notice that he manages to stay alive for a few seconds to utter his 'last words'. While actually, Lambert pretended to die and waited for Sam to leave. Then, he made his escape. Lambert felt deeply betrayed by Sam putting the mission before him, and spent the time between Double Agent and Blacklist plotting his revenge. Getting a reverse negroplasty, changing his voice, fabricating involvement with MI-6, and setting up a terrorist group: The Engineers. This also explains how the Engineers were able to disable the Paladin. Lambert (Sadiq) had knowledge of Third Echelon technology. Fourth Echelon kit is likely largely comprised of upgraded 3E kit, so Lambert was able to provide the information on how to disable the Paladin to Engineer hackers. Lambert orchestrated the Blacklist because he knew Sam would eventually get involved, and they would eventually meet. So in truth, the goal of the Engineers wasn't removing US soldiers from foreign soil. It wasn't initiating continuity of government at Site F. It was killing Sam. But it failed, so all this is rendered inconsequential. The Names of 12 Nations supporting the Engineers
These are surely Iran (because of Quds commandos present even AFTER the Iran mission), Russia (because of several guns like the SVU or Saiga-12K used only by Russian Spetnatz), UAE (because of massive money and F40 pistol) and probably North Korea,Yemen,Egypt,Pakistan, Syria,Belarus,Lebanon,Tajikistan,Turkmenistan (ok, this is just guessing based on actual hatred towards the US by this countries.). I will modify it if I found more elements.