New Islamic State efforts to sow terror in Europe are pushing counterterrorism authorities to their limits, forcing citizens and their leaders to resign themselves to a new era where attacks may be a fact of life, not an exception.

European Union leaders say they have swept away barriers among security agencies and bolstered border controls in the wake of a year of terrorist attacks capped by the assault on one of Berlin’s bustling Christmas markets. But missed signals before and after Monday’s violence raises questions about whether the changes — or any changes — are enough to prevent a repeat of a year that saw a double-bombing in Brussels, slaughter-by-truck in Nice, France, and shooting carnage in a Munich mall before the Berlin violence that killed 12 and wounded dozens more.

A call by Islamic State leaders for their followers to plan and carry out independent strikes against Europe bodes ill for efforts to stem the violence, officials and analysts say, given the practical barriers to constantly monitoring a large pool of potential attackers.

The changed terror tactics suggest that counterterrorism authorities may be successfully disrupting larger attacks, analysts say, offering a positive spin to the grim reality that small-scale violence may be inevitable.