IF nothing else, the Oklahoma City bomb tragedy has revealed to Americans that the terrorist threat from within is just as dangerous as the threat from without.
Extremist groups motivated by virulent opposition to abortion, gun control, or the federal government have been spreading throughout the United States in recent years, experts say. The most radical adherents of this far-right fringe have increasingly turned to violence as an outlet for their rage.
Most of the members of these self-described militia groups may not want to do more with a weekend than plunk a few cans with a rifle. But their message of blame and paranoia drives some over the edge. Violence occurs when a ''true believer, driven by the ideology, takes it to its logical conclusion,'' says Rafe Ezekiel, a University of Michigan professor.
The idea of home-grown terrorism may come as a surprise to many in the US. For years the face of terrorism has been a foreign one, the result of years of news from the Middle East and Europe about car bombs, kidnappings, and hijacked airliners.
The news that the bombing of the Oklahoma City federal building is allegedly the work of a person or persons from the heartland of the country could well raise mixed emotions in the US.
On one hand, it points out that no nation is free of the twisted reasoning that causes some to resort to bombs or bullets for their political causes.
On the other, US citizens may judge a threat from a domestic source less frightening, due to the fact that it is something US law enforcement officials can more easily track and control.
And the FBI and local police will surely now redouble their efforts to investigate and infiltrate these groups, many of whom were not seen as national threats in the past.
''The heat will be on,'' says Robert Wood, a North Dakota State University professor who teaches a class on terrorism.
Although its roots are obscure, the current rise of far-right disaffection likely began in the early 1980s with the formation of militia groups in rural areas of the country.
Convinced that lawmakers in Washington no longer defend the Constitution of the US as they interpret it, these ''militias'' arm themselves with assault rifes and train to defend their homes from their enemies: the FBI, the Bureau of Alcohol, Tobacco, and Firearms (ATF), and the UN.
Danny Welch, director of Klanwatch at the Southern Poverty Law Center in Montgomery, Ala., says he knows of 17 states with militia groups, many of which have known connections to racists and white supremacists.
Welch's organizaton wrote Attorney General Janet Reno last October to warn her of what it judges the growing militia menace.
Intense cynicism pervades
The militia movement is part political fervor and part John Wayne macho posturing, say experts. If it has a central tenet, it is hatred of the federal government, and specifically gun-control efforts that emanate from Washington.
Its martyrs are, among others, Gordan Kahl, a tax protester killed in a shootout with federal agents in 1983; and the 78 people who died at the Branch Davidian compound two years ago near Waco, Texas.
The ideology of militia members can be a confused jumble, with bankers, illegal immigrants, UN Secretary General Boutros Boutros Gahli, Attorney General Janet Reno, and other figures joined together in a loose perceived conspiracy against the white male way of life.
Such hatred is not new. The current US political climate may have given it more resonance, however, says the University of Michigan's Dr. Ezekiel.
Militia-spawned violence, he says, may be an outcropping of the intense cynicism people feel about the federal government, a ''loss of faith that makes people on the wobbly extremes of society even wobblier.''
People who join these groups are often on the margins of society. They are disaffected with life and want to feel powerful, says Danny Welch of the Southern Poverty Law Center. Add the fact that many of them have had military training, he says, and it's a ''recipe for disaster.''
Economics plays a large role as well, he notes. More people in rural areas are in economic trouble and contemptuous of the federal government. ''When you're hungry, he says, you're going to look for someone to blame.''
Even though militia groups are denying responsibility for the Oklahoma City attack the seedy side of this movement might drive some of the more stable people out. Many of them might recognize the absurdity of calling themselves a militia to protect the state.
''When was the last time we needed the militia, 1775?,'' says Welch.
Laws and public education needed
What can 100 men with rifles really do against a modern army, anyway? While Welch says militias can seem laughable, ''add hatred and automatic weapons and the the laughter ends.''
In the near term, Welch says that states have to consider adopting laws that forbid paramilitrary training, or repealing antiquated laws, like one in Arizona, that allow citizens to form armed groups. The public also has to be educated about issues concerning militias, and about the second amendment.
Both Ezekiel and Welch note that these groups feel provoked, and that in some ways, they are already at war with the government.
US law enforcement officials are now investigating whether, in fact, a conspiracy existed among a number of militia groups to carry out the attack on the Oklahoma City federal building.
Suspect Timothy McVeigh has been linked to the Arizona Patriots, a right-wing group once accused of planning to blow up an Internal Revenue Service building in Utah, as well as the Michigan Militia, a fast-growing group headquartered in the northern part of Michigan's lower peninsula.
For their part, Michigan Militia leaders strongly deny any part in the Oklahoma City attack and say that McVeigh was never a real member of their group.
Some militia members admit that McVeigh was present at group meetings.
Michigan Militia leaders held a long-planned rally in celebration of their one-year anniversary over the weekend. Asked if he felt his groups shared any blame for the Oklahoma City events, Michigan Militia chief of staff Ray Southwell said ''absolutely not.''
Southwell said that blaming his group was akin to blaming the US Post Office for deranged postal workers that fire on their fellows, or holding the National Collegiate Athletic Association responsible for any vandalism that followed in the wake of the UCLA victory in the NCAA basketball tournament last month.
Southwell, however, also condemned ''the terrorists within our federal government . . . for their role in the deaths of Branch Davidian members in Waco, Texas.''
''While senseless violence serves no purpose, we pray that this tragedy in Oklahoma will shake the halls of government,'' Southwell said.
Terry and James Nichols, brothers held as material witnesses in the Oklahoma City investigation, have also been linked to the Michigan Militia.
The basic beliefs of Michigan Militia members are grounded in a conviction that the UN is poised to overthrow the sovereignty of the US.
Members believe that large numbers of UN troops are massed on US military bases in preparation for attack and that highway signs may contain coded messages to guide the foreign troops.
Powerful individuals within the federal government are helping the UN, militia members believe, by eroding constitutional rights -- especially the right to bear arms.