From terror squads who slip past border controls to the valiant but all-too-improvised emergency response, the backstory of last week's attacks in Brussels is eerily similar to what happened in the United States in the leadup to September 11, 2001.
Virtually every mistake made then by the US national security machine found its analogue in Belgium on March 22. Now Europe's leaders need to work out their own answers to those challenges while overcoming particularly European obstacles. Until they do, their citizens will remain exposed to the next atrocity.
While much has been made of Belgium's failings - the split between Dutch- and French-speaking subcultures, interlocking layers of government that obscure accountability, the neglect of aggrieved Muslim communities - they are a microcosm of what Europe has to contend with. National security in the EU is just that: a national prerogative.
It comes down to "typical gumshoe detective-type work", said Colin Clarke, a terrorism researcher at Rand Corp in Pittsburgh.
"European intel services definitively have more suspects that they need to track, monitor and surveil.