BRUSSELS — A long-awaited offensive this week to dislodge the Islamic State from its stronghold city of Mosul is fueling fears of renewed terrorist attacks, as European counterterrorism officials say more fightersare returning home after waging jihad in Syria and Iraq. The security concerns are a major focus of European intelligence agencies as the Iraqi army and its partners press the assault on Mosul, which the Islamic State has used as a capital for planning and operations for more than two years.
Counterterrorism officials say it is too early to know whether the Mosul operation will spark a new wave of fighters coming back to Europe. But they say that when the Islamic State has been dealt battlefield blows in the past year, more of its adherents have returned home.