One of the keys to defeating the Islamic State (ISIS) is acquiring intelligence on it. So when a Syrian ISIS defector passed over a memory stick of names, telephone numbers and addresses of ISIS fighters to the United Kingdom broadcaster Sky News, it was a potentially significant moment.

The registration forms are taken from border crossings between November—December 2013 and acquired from ISIS’ internal security offices. Aspiring jihadists were required to fill in their personal details in order to be considered for membership.

Recruits from over 50 countries did so, proving that ISIS was not just a Syrian/Iraqi phenomenon even back then.

Western recruits are among those listed in the documents. That includes the deceased (British citizens Reyaad Khan and Junaid Hussain, both now killed in drone strikes) as well as those possibly still operational, such as Abdel-Majid Abdel Bary (a Londoner whose father was an associate of Osama bin Laden’s).

As for the others, the appropriate intelligence authorities will be running down leads, cross-referencing names and aliases. Some, inevitably, will be terror suspects who were already on the intelligence radar and various terrorism watchlists. Others, just as inevitably, will have slipped under the radar entirely. This may include Americans citizens, who are also known to be among the nationalities of those identified in this leak.

It must be hoped that these documents can prevent future ISIS atrocities. As we move further away from ISIS’ deadly attacks in Paris, the anger abates and the policy debate moves on. Yet ISIS has not.

The group remains as dedicated as ever to striking in the West and if it could inflict even greater casualties than it did in Paris, it doubtless would.

He claims to have left the groups because ISIS’ enforcement of religious law has “totally collapsed” and that the group is dominated by Baathists formerly loyal to Saddam Hussein

It must also be hoped that the factors that persuaded this defector to betray ISIS can persuade others to also turn against them. He claims to have left the groups because ISIS’ enforcement of religious law has “totally collapsed” and that the group is dominated by Baathists formerly loyal to Saddam Hussein (indeed, the Baath connections within ISIS are well-established.)

Yet a comprehensive defeat of ISIS cannot occur without a much more coherent approach to improving the situation in Syria and Iraq; and there is another aspect raised by this Syrian defector which should have a strategic—as opposed to solely counter-terrorism—impact on our approach to Syria. He claims that ISIS, Bashar al-Assad and the Kurdish YPG (People’s Protection Units) are essentially collaborating to wipe out the moderates in the Syrian opposition.

The YPG has been militarily backed by the US and proven itself to be an effective fighting force against ISIS. Yet this same group has been given air cover by Russia and is thought to be attacking the very same Syrian rebels that the CIA trained. Ongoing military backing of the YPG over moderate Arab rebel groups who are more focused on fighting the Assad regime is extremely questionable, to say the least.

The U.S. faces a host of difficult choices in Syria. Yet ultimately, as long as the conflict goes unresolved, ISIS will always manage to recruit and isolated defections offer occasional victories in the context of a broader strategic defeat.