Militia groups are independent survivalist paramilitary organizations that maintain an arsenal and grounds for training, usually in the context of espoused political beliefs in opposition to the government.

Many anti-US government "militias" developed within the United States during the 1970s and 1980s, and experienced wave of growth in the 1990s.

There is not a simple definition of how a group qualifies as a militia. However, the following general criteria can be used as a guideline: (1) a militia is a domestic organization with two or more members; (2) the organization must possess and use firearms; and (3) the organization must conduct or encourage paramilitary training. Other terms used to describe militias are Patriots and Minutemen.

Most militias engage in a variety of anti-government rhetoric. This discourse can range from the protesting of government policies to the advocating of violence and/or the overthrow of the federal government. However, the majority of militia groups are non-violent and only a small segment of the militias actually commit acts of violence to advance their political goals and beliefs. A number of militia leaders, such as Lynn Van Huizen of the Michigan Militia Corps -Wolverines, have gone to some effort to actively rid their ranks of radical members who are inclined to carry out acts of violence and/or terrorism. Officials at the FBI Academy classify militia groups within four categories, ranging from moderate groups who do not engage in criminal activity to radical cells which commit violent acts of terrorism. It should be clearly stated that the FBI only focuses on radical elements of the militia movement capable and willing to commit violence against government, law enforcement, civilian, military and international targets. In addition, any such investigation of these radical militia units must be conducted within strict legal parameters.

Militia anxiety and paranoia specifically relating to the year 2000 were based mainly on a political ideology, as opposed to religious beliefs. Many militia members believed that the year 2000 would lead to political and personal repression enforced by the United Nations and countenanced by a compliant U.S. government. This belief is commonly known as the New World Order (NWO) conspiracy theory. Other issues which have served as motivating factors for the militia movement include gun control, the incidents at Ruby Ridge (1992) and Waco (1993), the Montana Freemen Standoff (1996) and the restriction of land use by federal agencies.

One component of the NWO conspiracy theory -- that of the use of American military bases by the UN -- is worth exploring in further detail. Law enforcement officers, as well as military personnel, should be aware that the nation's armed forces have been the subject of a great deal of rumor and paranoia circulating among many militia groups. One can find numerous references in militia literature to military bases to be used as concentration camps in the NWO and visiting foreign military personnel conspiring to attack Americans.

Odinism is another white supremacist ideology that lends itself to violence and has the potential to inspire its followers to violence in connection to the millennium. What makes found on the website for the militia group United States Theatre Command (USTC). The USTC website prominently features the NWO theory as it portrays both Camp Grayling in Michigan and Fort Dix in New Jersey as detention centers to be used to house prisoners in an upcoming war. Specifically in reference to a photograph of Camp Grayling, the USTC website states: "Note that the barbed wire is configured to keep people in, not out, and also note in the middle of the guard towers, a platform for the mounting of a machine gun." Specifically in reference to a photograph of Fort Dix, the USTC website states: "Actual photos of an 'Enemy Prisoner of War' camp in the United States of America! (Fort Dix, New Jersey to be exact!) Is there going to be a war here? Many more are suspected to be scattered throughout the United States."

See also: Christian Identity, The Turner Diaries, Conspiracy theory