It didn’t start or end with Timothy McVeigh killing 168 people and wounding more than 680 others by detonating a fertilizer bomb in front of the Alfred P. Murrah Federal Building in Oklahoma City on April 19, 1995.

America’s divisions are fought over in many places. Courtrooms, the ballot box, on TV and protests in the streets. They’re also fought over by armed men and women - some in camouflage not issued by the federal government - far from the centers of population and power.

After McVeigh, the modern militia movement in the United States virtually disappeared, J.J. MacNab, an expert on domestic extremism, said in an extended interview. The toll was just too high for most and the clampdown by authorities was largely successful. But the movement - or movements - have grown again. In recent years, gun sales have grown, with only 3 percent of Americans owning half of the guns. Militias have reappeared, forming around people who claim the federal government is holding land illegally and collecting fees and taxes it has no rights to.

It goes beyond the famous Bundy family, who had success in standoffs with the federal government in Nevada, though less in Oregon. It’s a much larger group who call themselves sovereign citizens and believe only their own interpretation of the U.S. Constitution. It’s tax protesters. It’s racial separatists. Some of them are violent; some of them are elected officials; and some just pretend to be. This week’s War College looks into just how dangerous these groups are.

CORRECTION: An earlier version of this article incorrectly stated that only 3 percent of Americans had made most recent gun purchases. It is 3 percent who own half of all guns.