On Sept. 12, 2001, Defense Secretary Donald Rumsfeld said that "what we are seeing is the definition of a new battlefield in the world, a twenty-first century battlefield."

On Sept. 16, 2001, Vice President Dick Cheney said that America would have to "spend time in the shadows" and work on the "dark side."

Since then the U.S. has been engaged in a global war on terror, but Americans haven't known how exactly it is being fought.

That changed on Tuesday with the publication of "Dirty Wars: The World Is A Battlefield" by investigative journalist and New York Times bestselling author Jeremy Scahill.

Based on years of on-the-ground research and countless interviews, "Dirty Wars" details how Rumsfeld and Cheney began covertly deploying lethal tactics including black ops, secret prisons, snatch operations, and political assassinations at an unprecedented level.

From "Dirty Wars":

As The World Trade Center towers crumbled to the ground, so too did the system of oversight and review of lethal covert ops that had been carefully constructed over the course of the previous decade.

In place of that system, Scahill writes, a "War Council" led by Cheney advisor and fellow neoconservative David Addington developed legal justifications for capturing, torturing, and/or killing any al Qaeda suspect anywhere in the world.

The system became known as the "Cheney Program."

On September 17, 2001, George W. Bush signed a presidential finding that was used to create Greystone — a highly classified program outside of Congressional oversight that effectively "declared all covert actions to be pre-authorized and legal."

"I had never in my experience been part of or ever seen a presidential authorization as far-reaching and aggressive in scope," John Rizzo, a CIA veteran who helped draft the authorization, said. "It was simply extraordinary."

The most significant part, Scahill reveals, is that Greystone was not directly run by the president but by a small cadre of advisors led by Cheney.

Greystone became the umbrella under which authorization for targeted killing was streamlined — operations no longer needed direct presidential approval — and a global torture network involving "black sites" in at least eight countries.

"We deliberately kept the circle of people who knew where the black sites were to a very small number," Jose Rodriguez, the CIA official who coordinated the construction and use of the black sites, told Scahill. "As far as I know, the location of the black sites was not even shared with the president*."

What came next, Scahill writes, is the development of "the most effective kill and capture machine the world had ever seen* — one that, by it's very nature, would answer to no one but the president and his inner circle."

Check out an interview of Scahill by Democracy Now! >

Check out a sample of "Dirty Wars" published by The Nation >

*Emphasis added by the author of this article.