The 'Battle of the Rapido River' was fought between US and German forces in the course of one of the Allies' several attempts to breach the 'Winter Line', and despite its name was actually fought on the Gari river (2/22 January 1944).

Elements of the US 36^th Division, commanded by Major General Fred L. Walker, crossed the Gari river in boats and seized the river’s western bank. However, the US forces were then cut off from reinforcement and subjected to heavy fire and counterattacks from elements of Generalleutnant Eberhardt Rodt’s 15^th Panzergrenadierdivision. The 36^th Division suffered very high losses, and after two days of fighting the survivors retreated back across the river.

Late in 1943, the Italian campaign had reached a turning point. The Allied advance to the north through Italy bogged down around Monte Cassino, which was a crucial point in the Axis defensive position known as the 'Gustav-Linie', the most important of the three German defensive lines constituting the 'Winter Line'. As a result, Allied commanders planned to outflank the Germans with 'Shingle', an amphibious landing at Anzio between the 'Gustav-Linie' and Rome. To assist in the landing, Allied forces to the south were to launch attacks in the days leading up to 'Shingle' by seizing German positions across the Garigliano and Rapido rivers in the hope that this would result in the movement of forces from the Anzio area to the south in order to counter these attacks. However, the simultaneous attack at Anzio limited the availability of air support for the river crossings.

Lieutenant General Mark W. Clark, commander of the US 5^th Army, ordered a crossing of the Gari river, to the south of Monte Cassino, by the 141^st Infantry and 143^rd Infantry, both of these being regiments of the US 36^th Division in Major General G. Keyes’s US II Corps. After a bridgehead had been secured, an armoured advance was to strike across the Liri river valley.

On the night of 20 January, the US 36^th Division fired an artillery barrage of 31,000 rounds on German positions across the Gari river, causing only negligible damage. Feint attacks were conducted by Major General Charles W. Ryder’s US 34^th Division to the north, near Monte Cassino, to divert attention from the main advance. After the barrage had ended, the 141^st and 143^rd Infantry were ordered to cross the river at 19.00. Initial casualties were inflicted on the Allies by landmines on the river’s eastern bank, despite the efforts of army engineers tasked with clearing the approaches to the river. German artillery fire responding to the barrage also landed hits on elements of the 141^st Infantry before it was able to reach the river. Two infantry companies of the 143^rd Infantry successfully crossed the river, but German return fire resulted in the loss of too many men and landing boats, and the regiment’s foothold was abandoned. The 141^st Infantry fared still worse, being forced to withdraw with heavy casualties after landing directly in a minefield.

On the following day, both regiments were ordered to attack once again, beginning at 16.00. Although this assault met with more success, the US foothold was still unsustainable, as withering fire from the 15^th Panzergrenadierdivision, of General Fridolin von Senger und Etterlin’s XIV Panzerkorps within Generaloberst Heinrich von Vietinghoff-Scheel’s 10^th Army, prevented the construction of pontoon and Bailey bridges by engineers. Without the bridges, US armour could not assist in the attack, and the infantrymen were left to fight on their own, resulting in devastating casualties for the two regiments. After more than 20 hours of fruitless combat, both were ordered to withdraw. The 143^rd Infantry was able to withdraw relatively intact, but much of the 141^st Infantry was left stranded by the destruction of their bridges and boats by German fire. The Germans counterattacked the trapped Americans, capturing hundreds of soldiers. decided against committing his division’s last regiment, the 142^nd Infantry, and the battle concluded at 21.40 on January 22.

No significant gains had been made in either assault, and the original objective of luring away German forces was entirely unsuccessful.

Significant controversy followed the US defeat, with Clark criticising Walker’s execution of the battle plan. Walker responded that the entire battle had been foolhardy and unnecessary, and that Clark’s plan, against which Walker had protested, was all but guaranteed to fail. Otherwise known as the 'Battle of the Gari River', the 'Battle of the Rapido River' was one of the most significant defeats suffered by the US Army during World War II and was the subject of an investigation in 1946 by the Congress to establish responsibility for the disaster. Secretary of War Robert P. Patterson prepared a report in response to the Congressional investigation, in which he concluded that 'the action to which the Thirty-sixth Division was committed was a necessary one and that General Clark exercised sound judgment in planning it and in ordering it.' The president of the 36^th Infantry Division Association, testified before the Congress in opposition to Patterson’s conclusions and criticised what he perceived as Clark’s attempt to evade investigation of his conduct.