Under the leadership of Abu Musab al-Zarqawi, AQI was engaged in various militant activities during the early stages of the Iraqi insurgency, with the objective of expelling the U.S.-led coalition and establishing an Islamic state in Iraq.

The group was founded by Jordanian national Abu Musab al-Zarqawi in 1999 under the name Jama'at al-Tawhid wal-Jihad (Arabic: جماعة التوحيد والجهاد, lit.

After it pledged allegiance to Osama bin Laden's al-Qaeda network in October 2004, its official name became Tanzim Qaidat al-Jihad fi Bilad al-Rafidayn.

[17] In an online video, AQI gave Japan 48 hours to withdraw its troops from Iraq, otherwise Koda's fate would be "the same as that of his predecessors, [Nicholas] Berg and [Kenneth] Bigley and other infidels".

[34] Various parties participated during the civil war, but the main combatants were sectarian Shia and Sunni armed groups, such as the Islamic State of Iraq and the Mahdi Army, in addition to the Iraqi government alongside American-led coalition forces.

[42][43] In September–October 2005, there were signs of a split between homegrown Iraqi Sunni Arab insurgents who wanted Sunni influence in national politics restored,[44] and therefore supported a "no" vote in the 15 October 2005 referendum on a constitution,[45] and al-Zarqawi's Al Qaeda in Iraq, which strove for a theocratic state and threatened to kill those who engaged in the national political process with Shiites and Kurds,[44] including those who would take part in that referendum.

[30] American military field leaders, in particular, Lt. General Michael Flynn, in late spring 2004, were 'strategically surprised' at the capabilities, scale of operations, and quality of leadership of the subject.

[55] According to a report by US intelligence agencies in May 2007, the ISI planned to seize power in the central and western areas of the country and turn it into a Sunni Islamic state.

[57] In November 2004, al-Zarqawi's network was the main target of the US Operation Phantom Fury in Fallujah,[citation needed] but its leadership managed to escape the American siege and subsequent storming of the city.

[14] U.S. intelligence in October 2005 published an intercepted letter purportedly from Ayman al-Zawahiri questioning AQI's tactic of indiscriminately attacking Shias in Iraq.

[15] The affiliated groups were linked to regional attacks outside Iraq which were consistent with their stated plan, one example being the 2005 Sharm El Sheikh bombings in Egypt, which killed 88 people, many of them foreign tourists.

The Lebanese-Palestinian militant group Fatah al-Islam, which was defeated by Lebanese government forces during the 2007 Lebanon conflict, was linked to AQI and led by al-Zarqawi's former companion who had fought alongside him in Iraq.