On the basis of evidence thus far released by prosecutors, the group does not appear to have actually carried out any attacks. However, a host of signs suggest it is an especially violent and well-armed specimen of the paranoid anti-government groups that have been dragged into the spotlight over the past 14 months.
Foremost among these signs is what prosecutors claim is a 1994 video made by the group, amounting to a reconnaissance tour of targets in the Phoenix area - not only representatives of hated federal agencies like the Internal Revenue, the FBI, the US Secret Service and the Bureau of Alcohol, Tobacco and Firearms, but also buildings housing local law-enforcement bodies such as the Phoenix police, the Arizona national guard, as well as a television station.
A voice-over on the tape describes how each target could be destroyed, complete with details of the buildings' support structures, plans to destroy gas and water mains to hamper firefighters and rescuers, and for "anti-personnel" bombs to be planted in nearby mailboxes. These would explode as survivors tried to escape.
Nor was this idle talk. Police say that only two months ago, on 1 May, Viper Militia members claimed to have stockpiled 1,700lb of ammonium nitrate, the same ingredient which, mixed with fuel, made up the two-ton truck bomb that wrecked the Alfred P Murrah federal building in Oklahoma City, killing 168 people.
On Monday a six-month undercover infiltration scheme came to a climax with the arrest of 134 people, 11 men and two women. As they picked up the suspects at their homes, police found 400lb of the chemical as well as some 200 guns. A "potentially dangerous situation," had been defused, the Attorney General, Janet Reno, said.
Thus far no links have been established between the Viper Militia and the Oklahoma bombing. But the arrests only underscore the appeal of remote Arizona, with its frontier traditions, as a training ground for separatist groups, determined to avenge incidents like the FBI siege at Ruby Ridge, Idaho, in 1992 and the federal agents' assault at Waco the following year.
Far-right extremists are believed responsible for the October 1995 sabotage of the Sunset Express train as it crossed the deserts of western Arizona. The state was also home to Timothy McVeigh, one of the two men charged with carrying out the Oklahoma bombing. He is due to go on trial later this year.