Interview with investigative journalist JEREMY SCAHILL, author of "BLACKWATER: The Rise of the World's Most Powerful Mercenary Army."

Americans who pay attention to the news know that for four years, the U.S. has had a military force in Iraq ranging from 120,000 to 150,000 troops. That's half the truth, literally and figuratively. Your tax dollars are also funding a "shadow army" of 126,000 private security contractors, points out investigative reporter Jeremy Scahill in this riveting interview. Neither the deaths and injuries of this private half of the American troop presence, nor the crimes it commits, are part of the official story of the U.S. occupation.

One of the largest and most controversial contractors in this mercenary army is Blackwater USA, the North Carolina-based company best known for having four of its employees killed, burned, and hung from a bridge in Fallujah in 2004.

In conversation with host Tish Pearlman, Scahill lays out in compelling detail the story of Blackwater and its deep ties to both the government and the political right. He describes Blackwater's extensive role in government operations around the world and at home. For a time after Hurricane Katrina, Scahill says, the Department of Homeland Security paid Blackwater $240,000 a day for "security operations" in the Gulf. Blackwater paid its Gulf employees $350 a day while charging Uncle Sam almost three times as much.

Most importantly, Scahill makes a compelling case, grounded in solid reporting, that Blackwater and the rest of the private-sector army represent a threat to democracy, both in the U.S. and abroad. These are, he says, "unaccountable forces, waging war in our name, with our money."

These are strong claims and Scahill clearly has a point of view and, presumably, a left-leaning political bent. He's a reporter with Democracy Now and his book was published by Nation Books. But he mostly comes off as sober and solid, content to let his reporting speak for itself.

In her role as interviewer, Pearlman is not as restrained, and I suspect her tone will mar this interview for many program directors. Pearlman is a good host who asks the right questions, but she occasionally blurts out an emotional reaction. "That is really frightening." "My goodness, this is absolutely unbelievable." "It is very much like 1984." Call me old-school, but I think it's best to leave those reactions to the listener. Terry Gross would.