LONDON — In the weeks after Islamic State operatives struck Paris in November 2015, the group released a prerecorded video of the killers. They stared into the camera, waved serrated knives, raged at the West and specifically warned Britain: You’re next. Footage showed scenes of London through a gunsight.
For the next 13 months, the Islamic State and those inspired by the group killed and maimed in Brussels, Berlin, Nice and Normandy as well as across the Atlantic in California and Florida. Yet the rhetoric against Britain began to feel like the frothy threats made by the group toward other countries that had avoided attacks, including Iran: loud and menacing but ultimately empty.