The first phase, the initial transition between 2003 and 2007, started with a U.S.-led Coalition Provisional Authority. Each ministry had a U.S. advisor. As a self-declared occupying force, the U.S. military was responsible for national security, but at least 100,000 people died during its eight-year intervention (some estimates were as high as half a million). The transition included building new parties, recruiting and training new military forces, creating nascent civil society, and drafting new laws. In 2005, Iraqis voted on a new constitution, which introduced individual rights, including for religious and ethnic minorities.

The political balance of power—dominated for centuries by Sunnis—shifted dramatically. For the first time, the Shia majority claimed the prime minister’s slot and had sufficient leverage to control key ministries and other levers of the state. For the first time, Iraq also had a Kurdish president. Kurds, who had long demanded autonomy from Baghdad, became part of the state; the constitution recognized autonomy for the Kurdistan Regional Government (KRG) and formal status of its Peshmerga forces. Sunnis, who had dominated the state under Saddam, maintained the key position of parliamentary speaker but lost many other powers.

The transition also witnessed the outbreak of sectarian tensions, symbolized by the bombing of the al-Askari shrine, a Shia holy site, in early 2006. The blast destroyed the famous gold dome and triggered violence across Iraq for years. The tensions were exploited by Abu Musab al-Zarqawi, a Jordanian jihadi who had fought in Afghanistan and moved to Iraq to lead al-Qaida in Iraq. He was linked to bombings, kidnappings and beheadings. He was the first in a series of jihadi leaders determined to foment hostilities among Iraq’s ethnic and religious communities. Al-Zarqawi was killed in a U.S. airstrike in mid-2006. The group subsequently rebranded as the Islamic State in Iraq (ISI).

The second phase, from 2007 to 2011, was marked by the U.S. military surge of an additional 30,000 troops—adding to 130,000 already deployed—to help stem the escalating bloodshed. The surge overlapped with the so-called “Awakening” among Iraq’s Sunni tribes. They turned against the jihadi movement and started working with U.S. troops. The collaboration initially contained ISI. By 2011, the United States opted to withdraw from Iraq, with an understanding from the Baghdad government that it would incorporate the Sunni tribes into the Iraqi security forces to contain the sectarian divide.

The third phase played out between 2012 and 2017, as the government of Iraq did not follow through on promises to employ and pay the minority Sunnis who had fought the jihadis. Thousands of Sunnis were detained. By early 2013, tens of thousands of Sunnis participated in anti-government protests in Ramadi, Fallujah, Samarra, Mosul and Kirkuk. The Sunnis accused then Iraqi Prime Minister Nuri al-Maliki of exclusionary sectarian policies. Maliki’s relationship with the Kurds also deteriorated.

The Shia-dominated government’s failure to follow through with the Sunnis allowed ISI to reconstitute. The underground extremist movement recruited thousands of Sunnis, including beyond Iraq’s borders. In 2013, it expanded into Syria and rebranded again as the Islamic State in Iraq and Syria (ISIS). Its militia captured Fallujah in December 2013. Despite having far more numbers, the Iraqi army crumbled. By June 2014, ISIS took control of a third of the country. ISIS leader Abu Bakr al-Baghdadi declared the creation of an Islamic State in Mosul, Iraq’s second largest city, and named himself caliph. It instituted a reign of terror that included rape, abductions, executions, mass murder, pillaging, extortion, seizure of state resources, and smuggling.

The rise of ISIS further split Iraqi society. Grand Ayatollah Ali al-Sistani, the Shia world’s top marja, responded to the Sunni jihadis movement with a fatwa calling Iraqis to take up to arms. Tens of thousands of men, mostly Shia, joined new and old militias, many supported by Iran. More than 60 armed groups eventually merged under the umbrella of the Popular Mobilization Forces (PMF).

The rise of ISIS also led to foreign intervention a second time. Iran was the first to provide military assistance, partly because Sunni jihadis came within 25 miles of its border. In September 2014, the United States formed “The Global Coalition to Defeat ISIS,” made up of 79 countries and institutions, including NATO, the European Union, and the Arab League. The Obama administration re-deployed U.S. troops to retrain and advise the Iraqi Army; it also launched airstrikes that continued for more than three years until the Islamic State collapsed. Turkey deployed its own troops in northern Iraq to help protect Sunnis and Turkmen, but also to contain the influence of the Kurdistan Workers’ Party (PKK) that operated in both Iraq and Turkey.

Between 2015 and 2017, Iraqi security forces, Kurdish Peshmerga forces and the PMF—backed by airpower provided by the U.S.-led coalition—gradually retook territory from ISIS. Tens of thousands of jihadis reportedly were killed. In December 2017, Prime Minister Haider al-Abadi declared victory.

A fourth phase began in 2018 after the government regained control over all Iraqi territory. In May 2018, a national election redesigned the political landscape. Shia cleric Moqtada al-Sadr led an unlikely coalition with secular Sunnis and communists that won the largest number of seats while an Iran-backed block came second. Parliament elected veteran Kurdish politician Barham Salih as president and Muhammad al-Halbusi, a 37-year-old Sunni lawmaker, as speaker. Salih designated Adil Abdul al-Mahdi, a 76-year-old economist and veteran Shia politician to be prime minister.

Iraq’s turbulent transition reflected the wider changes and challenges across the Middle East in the 21st century:

• The biggest threat is not conventional warfare but asymmetrical conflict launched by militias and non-state actors. Despite losing its territory in 2017, ISIS remnants continued to attack civilian and military targets in Iraq. Jihadism remained a threat to several Arab governments by playing on Sunni grievances still not addressed by governments.
• Instability made Iraq vulnerable to regional and international rivalries. The U.S.-led invasion and occupation triggered deeper intervention by Iran. Tehran successfully applied its “Hezbollah” model in Iraq by supporting Shia armed groups, some of which began participating in Iraqi politics. Some groups—such as Harakat Hezbollah al-Nujaba, the Imam Ali Brigades and Asaib Ahl al-Haq—also became useful in Iran’s campaign to save the government of President Bashar al-Assad in neighboring Syria.
• For all its turbulence, Iraq’s transition produced some positive changes. Iraq reintegrated into regional and international forums. The number of media outlets increased dramatically. The long-repressed citizenry became politically active. Inspired partly by the 2011 Arab uprisings, Iraqis demonstrated to demand jobs and basic services. They also called out officials for corruption. Even amid the fight against ISIS in 2015, Iraqis pressured the government for reforms. One message from the 2018 election and previous demonstrations was that many Iraqis wanted to limit outside influence by Iran, Turkey and others. In 2018, Iraq produced oil at record levels. The economic wellbeing of many Iraqis improved, although unemployment and poverty were still serious problems.

Originally posted February 2019. Updated July 2019.

This timeline was assembled with the help of graphic research by Lindsay Jodoin and editorial research by Garrett Nada, Lindsay Jodoin and Eli Pollock.