The codenames for this battle are Operation Phantom Fury and Operation Al-Fajr. It was conducted by a coalition force involving America, Iraq and Britain. It was an offensive conducted in December 2004 and is considered the most intense engagement during the Iraq war in Fallujah. The Iraq insurgents had established a strong foothold in the city of Fallujah and the US Marine Corps led the coalition force to dismantle this foothold and free the city.

This operation received the approval and blessing and support from the Iraqi interim governed (which incidentally was appointed by the United States). The battle was termed as some of the most intense battles the Marines have fought since the Battle of Hue City during the Vietnam War.

The Second Battle of Fallujah followed the First Battle of Fallujah, where the coalition forces aimed to capture or kill dissident, insurgent factions that were responsible for the death of four Blackwater operatives. After the US military took over the city post the First Battle, the government asked the military to return leadership back to the local government in that city. After this, the local security forces began to build its defenses and stockpile weapons throughout the middle of 2004.

The Second Battle of Fallujah is considered the bloodiest. The fact that it was fought solely against insurgents and not the soldiers of the deposed Baath government is profound.

Once it was certain that the battle would be fought, the coalition force created checkpoints all around the city, cutting access to the city by anyone outside. They also prevented any insurgent from running away. Overhead satellite imageries were generated and the attackers were intimated on the detailed plan of the city. Furthermore, interpreters of the Iraqi language were attached to units to help them as they planned for their attack.

After withstanding several weeks of air bombardment, it was concluded that the city and its insurgents were vulnerable to direct attack. The coalition force tasked with taking down Fallujah amounted to more 13,000 troops. These troops were collected from the US military, the Iraqi military and the British military. More than 6,000 troops were Marines, more than 1,000 were from the Army, while more than 2000 were Navy.

The insurgent forces were made up of about 500 fulltime hardliners, and more than 1000 part-timers. This number was as at April. It was recorded that the number had multiplied by two at the end of November. In fact, the estimate was pegged at over 3000 insurgents, pulled from every insurgent group in Iraq.

Before the attack, the insurgents had prepared the city for an American invasion. They had scattered the city with mines. They had dug trenches. They had built IEDs. In some cases they had booby trapped buildings that was set to trigger when the soldiers entered them. The insurgents equipped themselves with advanced weaponry, including M15s and M16s and even body armor. Streets were blocked and strong points were created so that coalition troops could be attacked by insurgents when they least expected it.