Oh, when it comes to torture, we can rule out actual proper interrogation, given the military (and CIA) were schooled enough to know the techniques developed by Hanns Scharff (which do not require violence or cruelty) are far more effective than enhanced interrogation. To the contrary, Rumsfeld actively sought to circumvent Geneva Convention proscriptions against torture, even trying to suggest waterboarding isn't torture. (Plenty of pundits, whether right-wing and trying to be macho, or left-wing and trying to demonstrate that they are being impartial, got waterboarded by SERE to get a first-hand experience, and they all found it was unbearable, traumatic and caused lasting -- possibly permanent -- psychological symptoms. It est, waterboarding looks, smells, waddles and quacks like torture.)

The only reason people were tortured by agents of the United States, either by the US armed forces, or by CIA in its extrajudicial detention and enhanced interrogation program, is because plutocrats with influence within the government wanted revenge over 9/11 and blamed every Arab Muslim in existence, and wanted them to suffer.

This doesn't necessarily inform the countless other war crimes that were committed in the global War on Terror, or Iraqi Freedom, but there really is no strategic or diplomatic reason to torture, so it had to be done for aristocratic kicks.