Following Wisconsin, some analysts reminded commentators that the far right is responsible for as many – if not more – attacks on US soil than religious-based extremists, and now poses the most significant domestic security threat. Indeed, prior to 9/11 the most damaging act of terrorism within the US was the bombing of a federal building in Oklahoma by militia sympathiser Timothy McVeigh, which resulted in 168 deaths and more than 800 injuries. Between 1990 and 2010 the far right committed 145 ideologically motivated homicide incidents in the US. Of these incidents, excluding the bombing in Oklahoma City, far-right extremists killed 180 people.

The data suggests that American far right groups have grown “explosively”, which is attributed to a potent combination of public anxieties over the financial crisis, the growth of conspiracy theories, the exploitation of fears over non-white immigration and the prospect of Obama securing a second term in office.

According to the SPLC, in 2011 the number of “hate groups” active in the US reached 1,018, 69% more than in 2000. The most striking growth has been within the “patriot” scene, which contains anti-government groups that cling to conspiracy theories and view the government as enemy number one. There were fewer than 150 of these (mostly inactive) groups in 2000. By 2011, there were almost 1,300. In fact, since 2009 this particular variant of the far right has grown at a rate of 755%.

While it is difficult to compare across borders, similar warnings have been voiced in Europe. Last year, the Federal Office for the Protection of the Constitution in Germany noted that while the number of people in far-right political parties had contracted to 22,000, the number of those involved in more combative and confrontational forms of far-right politics was on the rise: the number of rightwing extremists with a propensity to violence had increased to 9,800; the number of followers of more violence-prone neo-Nazi groups had risen to 6,000; and the number of street-based demonstrations had reached an all-time high.

Though less affected than other countries, from 2001 onward, authorities in the UK have similarly voiced concern over a rapidly evolving far-right scene. In recent years, at least 17 individuals who committed or planned acts of violence or terrorism, and who were linked to the far right, have been imprisoned. In 2009, the discovery of a network of rightwing extremists in England with access to an arsenal of weapons prompted London Metropolitan police to warn that far-right militants might attempt a “spectacular” attack. In the same year theEnglish Defence League (EDL) was born, introducing a new form of far-right politics that is less interested than its predecessors in elections, and more focused on rallying support through street-based confrontation and networks that transcend national borders.

Though often dismissed as alarmist, these warnings were partly validated in July 2011, when Breivik launched his politically motivated attacks in Oslo and on the island of Utøya. Shortly afterward, authorities in Germany discovered that a violent neo-Nazi cell – the National Socialist Underground (NSU) – had been responsible for at least a dozen murders. Then, in Florence, an activist connected to the far-right group Casa Pound shot dead two immigrant street traders in an unprovoked attack. While it might be tempting to treat the attack in Wisconsin in isolation, it is actually the latest in a series of acts of violence from individuals linked to far-right groups.

The perpetrators of these attacks are often dismissed as crazed and psychologically flawed loners. Perhaps this is because we have grown used to the security threat from religious extremists and tend to view their far-right counterparts as a loony fringe, rather than rational agents who are using violence to achieve certain goals. What Breivik in Norway,Gianluca Casseri in Florence, the “London nailbomber” David Copeland and Michael Page all share in common is that they arrived at violence following a longer involvement with far-right extremism.