Intelligence and police agencies in the West have been noticing a pattern in the movements of Islamic terrorists from the West who are veterans of ISIL (al Qaeda in Iraq and the Levant) operations in the “caliphate” (Iraq/Syria and a few branch locations in places like Pakistan, Libya, Somalia and Nigeria). Compared to al Qaeda, ISIL is sending far fewer trained, motivated and prepared Islamic terrorists back to the West to organize and carry out major attacks. Instead ISIL tries to encourage Western fans of ISIL to do whatever they can where they are. This has led to a lot of embarrassing failures and a few successful but small scale acts of violence in the West, usually by individuals acting alone via the ISIL suggestion.
Al Qaeda was different and by the late 1990s it became clear that al Qaeda was making a major effort to train Islamic radicals to be effective Islamic terrorists in their home countries or the West. This program led to a few spectacular attacks (like those of September 11, 2001) but for the effort expended between 1989 and 2001 there was not a lot to show for it. During that period nearly 100,000 people attended these al Qaeda camps, most of them in Afghanistan. There were also al Qaeda camps in Sudan and Pakistan. But the biggest one was outside Kandahar in southwest Afghanistan and apparently accounted for over a third of the al Qaeda graduates. Actually less than a third of those attending al Qaeda camps “graduated” (had a month or more of training and acquired useful terrorist skills). Most of the other trainees were shown how to use firearms and perhaps RPGs but not much else because al Qaeda believed these men had little potential for anything more complex. Only a few percent of those attending the camps were believed capable of becoming effective terrorists and only a hundred or so actually got to do anything with their training.
By 2002 the United States had figured out that most of the al Qaeda terrorists dealt with during the 1990s had gone through the al Qaeda training camps in Afghanistan. Most (if not all) of the al Qaeda captured in Afghanistan had also gone through those camps. It was also discovered, from the many trainee rosters captured, that the majority of the trainees who returned home never did anything about Islamic terrorism except, in some cases, talk about it. ISIL got started in 2013 and by late 2014 it was clear that ISIL was no al Qaeda when it came to training terrorists. The reality was that very few ISIL veterans returned home with any skills or motivation for terrorist acts or any sort of violence. It didn’t take long (thanks to lots of information on lots of ISIL veterans) to figure out that ISIL needed all the men it could get to hold and try to expand its “caliphate”. ISIL leaders soon discovered that running a new state was a lot more difficult than they believed, especially when many, if not most, of the Moslems they ruled were hostile (eventually) to ISIL, and often violently hostile. A lot of new ISIL recruits found themselves on occupation duty policing Moslem populations (conservative Sunnis) that should have been very pro-ISIL. This proved demoralizing for many new ISIL recruits. But at least occupation duty was a lot more survivable than combat duty, which often involved suicidal tactics. Not just suicide bombers but serving with groups of guys armed with rifles and RPGs and little military training. ISIL leaders had a difficult time just getting these “troops” to one place in large numbers. There a cleric would give a rousing speech about the imminent chance to martyr oneself for Islam and enter paradise. That was followed by charging into machine-gun and shell fire and perhaps even smart bombs from jets overhead. After a few weeks of this many surviving ISIL recruits decided they had had enough and wanted to go home. ISIL did not allow such resignations and ISIL was soon publicly executing dozens of deserters at a time for the crime of getting caught trying to leave. Many more made it out and were not about to brag about it when they got home. Some of these were tracked down by police and questions, which is how the ugly (for ISIL) truth was discovered.