The website said Abu Musab al-Zarqawi, a top ally of al-Qaida leader Usama bin Ladin, was the man who cut off Berg's head. The statement in the video was signed off with Zarqawi's name and dated 11 May.
Aljazeera article
This same Zarqawi who is claimed to be behind the revenge beheading has been in the news many times before this.
From a previous post on March 20:
U.S. forces intercepted a document sent to al-Qaeda leaders that quoted a "terrorist" named Zarqawi as saying the military coalition in Iraq is "suffocating" resistance efforts, Bush said in a weekly radio address marking the first anniversary of the invasion to topple Iraqi leader Saddam Hussein. "Zarqawi is getting the idea," Bush said. "Whatever it takes, we will fight and work to assure the success of freedom in Iraq."
Yes, I'd say we really got Zarqawi on the run. At the time of this particular document surfacing, there was some question about its authenticity. It's possible it was a fake attempt to make it look as though we were kicking some of that Arab ass.
It is also the same Zarqawi that the Pentagon wanted to go after no less than three times before the invasion of Iraq but was blocked by the White House from doing so.
Miserable failure.
....but hey, do what you want....you will anyway.