Here is a very brief summary of what the experts say about torture:
Torture actually reduces our national security
Most of those tortured were innocent
They were not tortured in order to prevent terrorist attacks, but to create a false justification for the war in Iraq (by creating a false linkage between Iraq and Al Qaeda) (and see this). Torture has also been used throughout history as a form of intimidation, to terrorize people into obedience. However, it is not yet clear whether or not this was one of the reasons that the Bush administration implemented a policy of torture.
The 9/11 Commission report was primarily based upon confessions from those who were tortured. However, none of the information from those who confessed is credible. For example, one of the main sources for the 9/11 Commission Report was tortured until he agreed to sign a confession that he was not even allowed to read. See also this, this, this and this.
Prosecuting those in the U.S. who created the torture program will REDUCE attacks against the U.S. and against American troops
Read all George Washinton’s articles on torture: http://georgewashington2.blogspot.com/search?q=torture