The Bundesnachrictendienst (BND) is far better at surveillance than is given credit for. The USA is quite dependent on them right now due to the continued gutting of the CIA . . . not that Obama listens when he doesn’t feel like it, mind you. The Bundesamt für Verfassungsschutz (BfV) is no joke either.
Hah. No, I don’t doubt the effectiveness of German intelligence. The STASI made the KGB look like a bunch of oafs...but you’re talking a lot of people potentially. There are 3 million Turks in Germany, suspect the number of recruits would be in the hundreds if not higher.
It’s a conceit of Western governments that they think they can keep a lid on organized insurgent groups within their own borders. There is this idea that it can be managed.
Which is crap, as evidenced by 9/11, the LAX shootings, Nidal Hasan, and the Tsarnaev Brothers proved.
Can’t say what the optimal answer is. If Germany wants to keep them in the corral, it better be a real one.