"Experts say the same broad motives are at play whether the target is a mosque in Perth or an asylum seekers’ shelter in Dresden or a synagogue in Pittsburgh. Attackers who identify as white, Christian and culturally European see an attack on their privileged position in the West by immigrants, Muslims and other religious and racial minorities. The difference now is that it is easier than ever for extremists to connect both domestically and across continents, according to Mr. Berger, the “Extremism” author. The entry point for radicalization is less narrow than it was during earlier waves of white supremacist action, when finding ideological fellow travelers typically required meeting in person. “This is a particularly strong wave,” Mr. Berger said, “and I think it’s being fueled by a lot of political developments and also by the sort of connective tissue that you get from the Internet that wasn’t there before that’s really making it easier for groups to be influenced and to coordinate, or not necessarily coordinate but synchronize over large geographical distances.” Heidi Beirich, director of the Southern Poverty Law Center’s Intelligence Project, said that given these international connections, it’s important to reconsider the nature of the threat. “We conceive of this problem as being a domestic one,” she said. “But that’s not the case.” The challenge for law enforcement will be to buck a sometimes myopic focus on Islamic extremism as the only driver of international terrorism. It may also require rethinking the legal framework for what constitutes terrorism: from violence that arises from a command and control structure to a looser definition that can account for a wider range of violent actors who share a common ideology. “They don't see themselves as Americans or Canadians, very much like the Christchurch killer didn’t see himself as an Australian; he saw himself as part of a white collective,” Dr. Beirich said. “It has never been the case that these people didn’t think in a global way. They may have acted in ways that looked domestic but the thinking was always about building an international white movement.”"