Whether he personally murdered Nick Berg or was the hideous act's mastermind, Abu Musab Zarqawi has long been a known quantity–and a target of U.S. action.
This March article on MSNBC that details various blown opportunities to capture Zarqawi makes for particularly devastating reading in light of Berg's monstrous execution:
Abu Musab Zarqawi, a Jordanian militant with ties to al-Qaida, is now blamed for more than 700 terrorist killings in Iraq.
But NBC News has learned that long before the war the Bush administration had several chances to wipe out his terrorist operation and perhaps kill Zarqawi himself ? but never pulled the trigger.
The article's main source–former National Security Council member Roger Cressey–is controversial, but there seems no doubt that the US had, and missed, many opportunities to capture or kill Zarqawi.