Who is the US fighting in Iraq?

A February 2006 report from the International Crisis Group which provides a detailed look at the evolution of the insurgency, and describes its four main groups: Tandhim al-Qa’ida fi Bilad al-Rafidayn (recently decapitated), Jaysh Ansar al-Sunna, al-Jaysh al-Islami fil-’Iraq, and al-Jabha al-Islamiya lil-Muqawama al-’Iraqiya. In Iraq, the U.S. fights an enemy it hardly knows. Its descriptions have relied on gross approximations and crude categories (Saddamists, Islamo-fascists and the like) that bear only passing resemblance to reality. This report, based on close analysis of the insurgents’ own discourse [particularly their websites], reveals relatively few groups, less divided between nationalists and foreign jihadis than assumed, whose strategy and tactics have evolved (in response to U.S. actions and to maximise acceptance by Sunni Arabs), and whose confidence in defeating the occupation is rising. [from MetaFilter.com]