The Iraq War was a protracted armed conflict that began with the 2003 invasion of Iraq by a United States-led coalition. The invasion regime toppled the government of Saddam Hussein. However, the conflict continued for much of the next decade as an insurgency emerged to oppose the occupying forces and the post-invasion Iraqi government. An estimated 151,000 to 600,000 or more Iraqis were killed in the first 3–4 years of conflict. The United States officially withdrew from the country in 2011 but became re-involved in 2014 at the head of a new coalition; the insurgency and many dimensions of the civil armed conflict continue.

The invasion began on 20 March 2003, with the U.S., joined by the United Kingdom and several coalition allies, launching a "shock and awe" bombing campaign. Iraqi forces were quickly overwhelmed as U.S. forces swept through the country. The invasion led to the collapse of the Ba'athist government; Saddam was captured in December 2003 and executed by a military court three years later. However, the power vacuum following Saddam's demise and the mismanagement of the occupation led to widespread sectarian violence between Shias and Sunnis as well as a lengthy insurgency against U.S. and coalition forces. The United States responded with a troop surge in 2007 to attempt to reduce the violence. The U.S. began withdrawing its troops in the winter of 2007–08. The winding down of U.S. involvement in Iraq accelerated under President Barack Obama. The U.S. formally withdrew all combat troops from Iraq by December 2011.

The 2003 invasion of Iraq lasted from 20 March to 1 May 2003 and signaled the start of the Iraq War, which was dubbed Operation Iraqi Freedom by the United States (prior to 19 March, the mission in Iraq was called Operation Enduring Freedom, a carryover from the War in Afghanistan). The invasion consisted of 21 days of major combat operations, in which a combined force of troops from the United States, the United Kingdom, Australia and Poland invaded Iraq and deposed the Ba'athist government of Saddam Hussein. The invasion phase consisted primarily of a conventionally fought war which concluded with the capture of the Iraqi capital of Baghdad by American forces.

160,000 troops were sent by the Coalition into Iraq, during the initial invasion phase, which lasted from 19 March to 9 April 2003. About 130,000 were sent from the USA alone, with about 28,000 British Soldiers, Australia (2,000), and Poland (194). 36 other countries were involved in its aftermath. In preparation for the invasion, 100,000 U.S. troops were assembled in Kuwait by 18 February. The coalition forces also received support from Kurdish irregulars in Iraqi Kurdistan.

Coordinates: 33°N 44°E / 33°N 44°E / 33; 44

Iraq (/ɪˈræk/, ⁱ/ɪˈrɑːk/, or /aɪˈræk/; Arabic: العراق‎ al-‘Irāq, Kurdish: Êraq), officially the Republic of Iraq (Arabic:  جمهورية العراق  Jumhūrīyat al-‘Irāq; Kurdish: كۆماری عێراق‎ Komar-i ‘Êraq), is a country in Western Asia. The country borders Turkey to the north, Iran to the east, Kuwait to the southeast, Saudi Arabia to the south, Jordan to the southwest, and Syria to the west. The southern part of Iraq is within the Arabian Peninsula. The capital, Baghdad, is in the centre of the country and its largest city. The largest ethnic groups in Iraq are Arabs and Kurds. Other ethnic groups include Assyrians, Turkmen, Shabakis, Yazidis, Armenians, Mandeans, Circassians, and Kawliya. Around 95% of the country's 36 million citizens are Shia or Sunni Muslims, with Christianity, Yarsan, Yezidism, and Mandeanism also present.

Iraq has a narrow section of coastline measuring 58 km (36 mi) on the northern Persian Gulf and its territory encompasses the Mesopotamian Alluvial Plain, the northwestern end of the Zagros mountain range, and the eastern part of the Syrian Desert. Two major rivers, the Tigris and Euphrates, run south through the centre of Iraq and flow into the Shatt al-Arab near the Persian Gulf. These rivers provide Iraq with significant amounts of fertile land.

The Kingdom of Iraq under British Administration or Mandatory Iraq (Arabic: الانتداب البريطاني على العراق‎ al-Intidāb al-Brīṭānī ‘Alá al-‘Irāq) was created in 1921 following the 1920 Iraqi Revolt against the proposed British Mandate of Mesopotamia, and enacted via the 1922 Anglo-Iraqi Treaty.

Faisal ibn Husayn, who had been proclaimed King of Syria by a Syrian National Congress in Damascus in March 1920, was ejected by the French in July of the same year. Faisal was then granted by the British the territory of Iraq, to rule it as a kingdom, with the British Royal Air Force (RAF) retaining certain military control, though de facto; the territory remained under British administration until 1932.

The civil government of postwar Iraq was headed originally by the High Commissioner, Sir Percy Cox, and his deputy, Colonel Arnold Wilson. British reprisals after the murder of a British officer in Najaf failed to restore order. The most striking problem facing the British was the growing anger of the nationalists, who continued to fight against the imposition of British authority. British administration had yet to be established in Iraqi Kurdistan.

Mesopotamia (/ˌmɛsəpəˈteɪmiə/, from the Ancient Greek: Μεσοποταμία "[land] between rivers"; from Ancient Armenian՝ Միջագետք(Mijagetq), Arabic: بلاد الرافدين‎ bilād ar-rāfidayn; Persian: میان‌رودان‎‎ miyān rodān; Syriac: ܒܝܬ ܢܗܪܝܢ‎ Beth Nahrain "land of rivers") is a name for the area of the Tigris–Euphrates river system, roughly corresponding to modern-day Iraq, Syria and Kuwait, including regions along the Turkish-Syrian and Iran–Iraq borders.

Widely considered to be the one of the cradles of civilization by the Western world, Bronze Age Mesopotamia included Sumer and the Akkadian, Babylonian, and Assyrian empires, all native to the territory of modern-day Iraq. In the Iron Age, it was controlled by the Neo-Assyrian and Neo-Babylonian Empires.

The indigenous Sumerians and Akkadians (including Assyrians and Babylonians) dominated Mesopotamia from the beginning of written history (c. 3100 BC) to the fall of Babylon in 539 BC, when it was conquered by the Achaemenid Empire. It fell to Alexander the Great in 332 BC, and after his death, it became part of the Greek Seleucid Empire.