Aryan Nation, the organisation linked to an alleged germ terrorism plot, is one of the groups stitched into the semi-organised miasma which makes up the extreme armed right wing in the US. It is often cited alongside the more infamous Ku Klux Klan.

Two men with links to the group, Larry Harris and William Leavitt, have been charged in Nevada after being arrested on Thursday in possession of a biological agent believed to be anthrax.

For a while, even within the labyrinth of the far right, Aryan Nation was considered a bit of a joke. The headquarters of its compound in Hayden Lake, Idaho, is a cramped log cabin festooned with swastikas, where guests are greeted by a former US Marine, Tim Bishop, kitted out in jackboots and leather webbing.

Sunday prayers are led by the man Bishop calls his Fuhrer, pastor Richard Butler, who preaches to the congregation about how the white race should never forget about its war with the Jews.

Those in search of waging that war - and others fought by the extreme right - appeared, however, to have drifted elsewhere, into the more cogent militia movement, which gift-wraps its affiliations with the old Klan and suchlike in more appealing, newer ideologies.

The most effective of these was the revolutionary struggle where by the militias claimed a descent from those who fought for America's freedom from the British Empire: that of free Americans against a central government which was no more than a tool of the "new world order", in turn controlled by an opaque occult cabal.

Within that umbrella was an organisation called Christian Identity, based at a compound called Elohim City, uncomfortably close to Oklahoma City, where a bomb was detonated in April 1995, killing 169 people.

Christian Identity was based upon the idea of training Christian families for a coming "racial apocalypse", in which believers would rid themselves from the yoke of rule by Jews and blacks, who were the devil's instruments for the contamination and destruction of society.

Their compound is a more severe and forbidding place, run by its commander and preacher, Robert Millar. Millar's sect bridges the far right and the militia movement, coming as it does from the microscopic fringes, but visited by Timothy McVeigh, convicted of the Oklahoma bomb.

Aryan Nation's role as prime mover within this axis was established by the fact that Randy Weaver, whose cause spawned the militia and Christian Identity movements, was a member.

Weaver, who refused to pay taxes or any kind of dues to the government, had turned his remote home into a stockade, withstanding an FBI and ATF siege for many days in 1992 before his wife and son were killed by sharpshooters. He became a martyr and inspiration to the movement.

While the militias took the limelight, Aryan Nation continued busily on the outskirts of the mainstream movement, keeping alive the bridge between the militias (some of whom even had black front-men) and the old die-hard factions.

The bomber of an abortion clinic in Georgia last month was a member of the group.

Aryan Nation targeted groups of disaffected youths in Colorado, detonating a spate of racialist murders in and around Denver at the end of last year. "We are living," said the family of one of the victims, "with the Aryan Nation at our gates."

The group has been busy on the Internet, posting numerous sites full of so-called "hate-speech", of the kind President Clinton targeted with a special task-force recently. Most sinister of all, though, the axis around Aryan Nation and Christian Identity became associated over the past few months with another US nightmare - domestic terrorism, using chemical and biological weapons that had hitherto been the province of renegade states like Iraq.

In 1993, Canadian police stopped an Aryan Nation member, Thomas Lavy, and found an arsenal of weapons and recipes for chemical weapons in his car.

Last November, an Aryan Nation member, James Bell, was found with a concoction of dangerous chemicals and a Terrorist Manual at his home in Oregon. The plot was openly based on that of the Aum Shinri Kyo sect in Tokyo, who tried to use anthrax to mount a horrific terrorist attack on the subway in the Japanese capital.

Microbiologist Larry Wayne Harris was arrested in Ohio, charged and put on probation for possession of vials of the bacteria which produce bubonic plague.

Ironically, Harris had warned in his many writings of an "invasion from Iraq" using chemical weapons. It now emerges that Harris, arrested yesterday for alleged possession of anthrax, is linked to both Aryan Nation and Christian Identity.

For some time, Capitol Hill has sought to prepare US citizens for a home-grown chemical and biological weapons attack. Wild-card Republican senator Richard Lugar has propelled a multi-million dollar programme to combat the threat in its many guises.

Mr Lugar's programme was propelled by intelligence that Iraqi squads were at large, armed with chemical weapons - but his efforts had no doubts about their use to the revolutionary right.

His programme ranges from instructing former Soviet states against the risks of "loose nukes" to training citizens how to protect themselves against the kind of spine-chilling attack that was planned for Tokyo and which Harris and his comrade appear to have been planning for New York.