This was the US crossing of the Rhine river in western Germany by Lieutenant General George S. Patton’s 3rd Army (22/24 March 1945).
On 19 March General Dwight D. Eisenhower, the Supreme Allied Commander of the Allied Expeditionary Force, had ordered General Omar N. Bradley, commanding the 12th Army Group, to prepare Lieutenant General Courtney H. Hodges’s 1st Army to break out of its Remagen bridgehead across the Rhine on or soon after 22 March. On the same day, responding to the excellent performance of the 3rd Army in the Saar-Palatinate region farther to the south and to gain the benefit of having another strong force on the Rhine river’s eastern bank shielding the 1st Army’s right flank, Bradley gave Patton the go-ahead for an assault crossing of the Rhine as soon as possible.
This was exactly the order for which Patton had hoped, for the 3rd Army’s commander believed that that if a force of sufficient strength could be thrown across the river and achieve significant gains without undue delay, then Eisenhower might transfer responsibility for the main drive through Germany from Field Marshal Sir Bernard Montgomery’s Allied 21st Army Group in the north to Bradley’s 12th Army Group in the centre. Another factor in Patton’s thinking was that his army now had the opportunity to beat Montgomery’s forces across the river and so win the distinction of making the first assault crossing of the Rhine in modern history. He also appreciated, though, that the accomplishment of this task demanded swift planning and fast action, both of these being matters in which his army was well versed.
On 21 March Patton ordered Major General Manton S. Eddy’s XII Corps to prepare for an assault over the Rhine on the following night, one day before Montgomery’s scheduled 'Plunder' crossing. Knowing the overall situation and the thinking of his army commander, Eddy had already started to plan for such as eventuality. As soon as Patton had received the order on 19 March to make a crossing, he had begun sending assault boats, bridging equipment, and other supplies forward from depots in Lorraine, where they had been stockpiled since the autumn of the previous year in the expectation of just such an opportunity. The location of the river crossing assault was critical. Patton knew that the most obvious place to jump the river was at the city of Mainz or just downstream of it, to the north of the city. The choice was obvious because the Main river, flowing northward some 30 miles (48 km) to the east of and parallel with the Rhine, turns west and debouches into the Rhine at Mainz, so any advance south of the city would involve the crossing of two major rivers rather than just one.
Patton realised that the Germans would also be aware of this difficulty, however, and would therefore expect the Americans to commit this river crossing operation north of Mainz. Thus Patton decided to make only a feint at Mainz while making his real effort at Nierstein and Oppenheim, 9 to 10 miles (14.5 to 16.1 km) south of the city. The primary assault crossing was entrusted to the XII Corps, with Major General Troy H. Middleton’s VIII Corps allocated to the task of making support crossings at Boppard and St Goar, 25 to 30 miles (40 to 48 km) to the north-west of Mainz.
With high ground on the western bank overlooking relatively flat land on the eastern bank, the terrain in the vicinity of Nierstein and Oppenheim was favourable to the use of potent artillery support. However, the same flatness of the eastern bank meant that the bridgehead would have to be rapidly and powerfully reinforced and expanded beyond the river since there was no high ground on which to establish a bridgehead defence perimeter. The importance of obtaining a deep bridgehead without delay was emphasised by the fact that the first access to a decent road network was more than 6 miles (9.7 km) to the east of the river at Grossgerau.
On 22 March, under bright moonlight, elements of the XII Corps' 5th Division, commanded by Major General S. LeRoy Irwin, began the 3rd Army’s crossing of the Rhine. At Nierstein the assault troops met no resistance from the forward elements of General Hermann Förtsch’s 1st Army within SS-Oberstgruppenführer und Generaloberst der Waffen-SS Paul Hausser’s Heeresgruppe 'G'.
As the first US boats reached the eastern bank, seven German soldiers surrendered and then paddled themselves unescorted to the western bank to become prisoners. Farther up the river, at Oppenheim, the US crossing did not proceed so casually. The first wave of boats was half way across the Rhine when the Germans began pouring machine gun fire into them. An intense exchange of fire lasted for about 30 minutes as assault boats kept pushing across the river and those men who had already made it across attacked and slowly eliminated the scattered defensive strongpoints. Finally the Germans surrendered, and by 24.00 US units were able to move out laterally to consolidate the crossing sites and to attack the first villages beyond the river.
Everywhere the resistance of the Germans was only sporadic and their counterattacks, mounted and implemented hastily, failed to drive the US units back to the river and caused only very modest casualties. The Germans lacked both the manpower and the heavy equipment to make a more determined defence.
By middle of 23 March’s afternoon all three regiments of the 5th Division had crossed into the bridgehead, and an attached regiment of Major General Lowell W. Rooks’s 90th Division was in the process of crossing. Tanks and tank destroyers had been ferried across all morning, and by evening a foot bridge was open to traffic. By 24.00, US infantry had pushed the boundary of the bridgehead well to the east ensuring the unqualified success of the first modern assault crossing of the Rhine.
Two more crossing by elements of the VIII Corps quickly followed. In the early morning hours of 25 March, units of Major General Frank M. Culin’s 87th Division crossed the Rhine farther to the north at Boppard, and then some 24 hours later units of Major General Thomas D. Finley’s 89th Division crossed 8 miles (13 km) to the south of Boppard at St Goar. Although the defence of these sites was somewhat more determined than that which the XII Corps had faced, the difficulties of the Boppard and St Goar crossings were caused more by the terrain than German resistance.
The VIII Corps' crossing sites were located along the Rhine Gorge, where the river has carved a deep chasm between two mountain ranges, creating precipitous canyon walls more than 300 ft (90 m) high on each side. In addition, the river flows quickly and with unpredictable currents along this part of its course. Despite the terrain and German fire from machine guns and anti-aircraft cannon, the men of the VIII Corps gained control of the eastern bank’s heights, and by dark on 26 Mach, with German resistance crumbling all along the line of the Rhine, the Allied forces were preparing to continue the drive the next morning.