For a year now, Al Qaeda-like terrorists have been inching up on Europe. In May, they attacked Jewish and Belgian targets in Morocco. In November, they went after Jewish and British targets in Istanbul.
With last week's attacks in Madrid, they reached Europe's core, adding a new dynamic that is stirring up populations, politics, and strategy about the best way to meet the terrorism threat.
Suddenly, Europeans are thinking more deeply about the implications of these bombings for them.
Will Madrid, or any future attack, have the power to overturn other governments (Italy, perhaps?) that have been staunch allies of the US war on terrorism?
Will the new leader in Spain feel more at home with his counterparts in Berlin and Paris, and reopen a transatlantic rift that is beginning to heal a year after the Iraq invasion?
An affirmative answer to both these questions would be regrettable.
On a more practical level, the Europeans also sense a new urgency to step up antiterrorism measures. Interior ministers of the European Union will meet in emergency session Friday to discuss this, and it will feature in next week's EU summit.
Since Madrid, individual countries have tightened security. They're good at that, given their histories with terrorist groups such as the IRA and the Red Brigades. But as EU foreign and security policy chief Javier Solana points out, EU members must cooperate more, such as in sharing intelligence. There's even talk of creating a European Central Intelligence Agency.
But Europe doesn't need more bureaucracy. It needs to better use the tools it has, such as Europol, created last year to improve cooperation among judicial officials. It also needs to fully implement its antiterrorism action plan, spawned by 9/11. Five countries, for instance, have yet to set in place a Europe-wide system for arrest warrants.
The current EU must also wrestle with carrying the antiterrorism fight to 10 new members joining May 1. This includes how to stretch a new EU wide border-security agency (also not yet implemented) to new members.
Madrid has the potential to set in motion the kind of reassessment in Europe that took place in America.