<P> The main two participants in the violence were the Arab Sunni and Arab Shia factions , but conflicts within a single group also occurred . The Kurds were caught between the two religious groups , but as they were an ethnicity as opposed to a religious movement , they were often at odds with the Arabs that were settled in Iraqi Kurdistan by Saddam 's Arabization policy . Blurring this cohesion , though , were division of social , economic , political and geographic identities . </P>
the primary ethnic factional groups fighting each other in iraq after the invasion were
Arab Sunni Arab Shia