The terrorist attack in New Zealand has focused attention once more on the acute threat posed by rightwing extremists.
Waves of terrorism follow a pattern: a long, unnoticed buildup followed by a massive and spectacular strike that often inflicts significant damage and casualties but focuses minds and eventually resources.
Counterterrorism agencies, driven by public outrage and concerned officials, struggle for a time to gain the upper hand until, with better funding and understanding, they begin to win the battle to keep us safe. The cycle can take many years, even decades.
Rightwing terrorism was building through the 2000s. The spectacular event came when the Anders Behring Breivik killed 77 people in Norway in 2011. Since then there has been a steady drumbeat of violence: the killing of 11 Jewish worshippers in Pittsburgh, the murder of the British MP Jo Cox, attacks on mosques in London and Quebec, and, barely reported, many more incidents motivated by hatred.