March 20–25, 2003 · Southern Iraq Theater

The first battle of the Iraq War, fought for the port city of Umm Qasr on the Persian Gulf coast — Iraq's only deep-water port. US Marines and British Royal Marines secured the port over five days of unexpectedly fierce resistance from Iraqi regular forces and Fedayeen Saddam paramilitaries. The battle was supposed to take hours; it took nearly a week, setting the first warning about Iraqi resistance. Coalition forces also cleared the harbor of mines to allow humanitarian aid ships to dock.

March 20 – April 9, 2003 · Central Iraq Theater

Operation Iraqi Freedom opens with 'Shock and Awe' — a night-time cruise missile and precision bombing campaign against Baghdad. Three US Army divisions and the 1st Marine Division drive north from Kuwait simultaneously. The 3rd Infantry Division reaches Baghdad's outskirts in 21 days. On April 5, 'Thunder Run' — a tank column charges straight through the city center — and the Republican Guard collapses. On April 9, a US military vehicle pulls down the statue of Saddam Hussein in Firdos Square before a watching world.

March 23 – April 2, 2003 · Southern Iraq Theater

The bloodiest battle of the conventional invasion. The 1st Marine Regiment fights through Nasiriyah — a vital bridge crossing over the Euphrates — in ten days of intense urban combat. On March 23, an Army maintenance convoy (507th Maintenance Company) makes a wrong turn into the city and is ambushed: 11 soldiers are killed and several captured, including Pfc. Jessica Lynch, whose rescue dominated US media for weeks. Marines then fight block by block through the city while Fedayeen snipers and ambushes from civilian areas kill 18 Marines in a single day.

April 1–3, 2003 · Central Iraq Theater

The Karbala Gap — a 20-mile wide corridor between Karbala Lake and the Euphrates River — was the gateway to Baghdad and the point where Republican Guard planners expected to halt the American advance. Sandstorms and logistics delays gave Saddam's defenders time to prepare. The 3rd Infantry Division passed through the gap in a night attack on April 1–2, outmaneuvering and destroying Republican Guard units in what proved to be the decisive engagement before the dash to Baghdad. US commanders had feared chemical weapon use in the gap; it never came.

April 4–May 1, 2004 · Al Anbar Province Theater

After four Blackwater contractors are killed and their bodies hung from a bridge in Fallujah, the Marine Corps launches an assault on the city. Three days in, with Marines fighting street by street, US political leadership halts the operation under Arab pressure — allied Iraqi Governing Council members threaten to resign. Marines, who had taken 27 killed in three days of fighting, are ordered to halt and hand the city to an Iraqi force that promptly defects to the insurgency.

November 7 – December 23, 2004 · Al Anbar Province Theater

Operation Phantom Fury — the largest urban battle of the Iraq War. Marines and Army troops assault Fallujah in the most intense house-to-house combat since Hue City in Vietnam. The city has been fortified with IED networks, booby-trapped buildings, and interconnected tunnel systems. After six weeks of fighting, the city is cleared — 95 Marines and soldiers killed, 560 wounded, and 1,350 insurgents killed. Much of the city is destroyed.

November 10–14, 2004 · Northern Iraq Theater

While American attention focused on Fallujah, insurgents launch a coordinated uprising in Mosul. Iraqi police and security forces — 5,000 men — collapse almost entirely in 24 hours. Police stations are seized, weapons depots looted. Only about 500 of 5,000 Iraqi police officers report for duty. The 25th Infantry Division rushes to Mosul and eventually restores order, but the city falls into a cycle of insurgent control and US counter-operations.

2006 – March 2007 · Al Anbar Province Theater

Ramadi, capital of Al Anbar Province and population center of Iraq's Sunni heartland, was effectively controlled by Al-Qaeda in Iraq by early 2006 — a city of 400,000 people that US commanders privately described as lost. Col. Sean MacFarland's 'Ready First' brigade arrived in June 2006 and implemented an aggressive strategy: moving soldiers off large bases and into combat outposts inside the city, partnering with any Sunni tribal leader willing to resist AQI, and systematically clearing neighborhoods block by block. The Sunni Awakening began here when Sheikh Abdul Sattar Abu Risha allied with MacFarland in September 2006.

March 23 – May 12, 2008 · Baghdad Theater

Sadr City — a Shia slum of 2.5 million people in northeastern Baghdad, stronghold of Muqtada al-Sadr's Mahdi Army — becomes a battleground when Iraqi government forces attempt to dismantle militia control. US Army engineers construct a concrete barrier wall across the city's southern boundary to separate the militia stronghold from the rest of Baghdad, while American and Iraqi forces fight daily skirmishes with JAM fighters launching rockets and mortars into the Green Zone. After 49 days, a ceasefire is negotiated and the wall construction completed.

March 25 – April 20, 2008 · Southern Iraq Theater

Operation Charge of the Knights — Prime Minister Maliki personally flies to Basra to lead Iraqi Security Forces in a major assault on the Mahdi Army, which controls large parts of southern Iraq. The initial assault goes badly — ISF units mutiny or are badly mauled. US air strikes and Special Forces trainers are rushed in. After three weeks, the Mahdi Army accepts a ceasefire. Sadr stands down his forces, claiming victory.