The Karbala Gap was a 20-25-mile wide strip of land with the Euphrates River to the east and Lake Razazah to the west. This strip of land was recognized by Iraqi commanders as a key approach to Baghdad, and was defended by some of the best units of the Iraqi Republican Guard. The Iraqi high command had originally positioned two Republican Guard divisions blocking the Karbala Gap. Here these forces suffered heavy Coalition air attacks. However, the Coalition had since the beginning of March been conducting a strategic deception operation to convince the Iraqis that the US 4th Infantry Division would be mounting a major assault into northern Iraq from Turkey.

This deception plan worked, and on April 2 Saddam's son Qusay Hussein declared that the American invasion from the south was a feint and ordered troops to be re-deployed from the Karbala front to the north of Baghdad. Lt. Gen. Raad al-Hamdani, who was in command of the Karbala region, protested this and argued that unless reinforcements were rushed to the Karbala gap immediately to prevent a breach, American troops would reach Baghdad within 48 hours, but his suggestions fell on deaf ears. American troops rushed through the gap and reached the Euphrates River at the town of Musayib. At Musayib, American troops crossed the Euphrates in boats and seized the vital al-Kaed bridge across the Euphrates after Iraqi demolitions teams had failed to destroy it in time.

The 10th Armored Brigade from the Medina Division and the 22nd Armored Brigade from the Nebuchadnezzar Division, supported by artillery, launched night attacks against the American bridgehead at Musayib. The attack was savagely repulsed using tank fire and massed artillery rockets, destroying or disabling every Iraqi tank in the assault. The next morning, Coalition aircraft and helicopters rained death on the Republican Guard units, destroying many more vehicles as well as communications infrastructure. The Republican Guard units broke under the massed firepower and lost any sense of command and cohesion and the American forces poured through gap on to Baghdad