It is plausable, nay, probable that the Terrorists that have "invaded" Fallujah, have ALWAYS lived there. That Saddam Hussein himself may have had to deal with such Terrorists.
Given the: "If the enemy fights from mosques, level the mosques. If they fight from hospitals, gut the hospitals. If they open fire from orphanages, turn them into blackened shells." - isn't it possible that Saddam's mass murder gravesites were the direct result of Saddam's attempts to deal with these Terrorists?
Perhaps those mass murder gravesites were justified.