The battle of the Rapido River (20-22 January 1944) was part of the wider first battle of Cassino, and was a costly failure that had to be abandoned after only two days.
The overall Allied plan in January 1944 was for a four pronged assault on the German position on the Gustav Line. Three were part of the first battle of Cassino, and took place on the main fifth army front. The fourth was the landings at Anzio, behind the German lines. The plan was for the French to attack north of Cassino on 12 January and take the high ground north of the planned crossing point. The British would attack to the south a few days later, leaving the Germans on the Rapido trapped between two Allied forces. The US 36th Division would then attack across the river, and establish a bridgehead into which the US 1st Armoured Division could advance and then break out west into the Liri Valley. The Rapido would be crossed on 20 January, two days before the landings at Anzio, to allow enough time for the American troops to begin their advance towards the new beachhead.
No part of this plan went as expected. The French attack began on 12 January, but had to be abandoned after four days, having limited progress. The British attack went a little better, and they were able to cross the Garigliano River (formed when the Rapido met the Liri), but they were unable to capture the crucial high ground. As a result the American troops attempting to cross the Rapido were unsupported on both flanks.
Despite these failures, Clark decided to go ahead with the attack across the Rapido, in the belief that it would prevent the Germans from moving any troops from the Cassino front to Anzio. General Walker, the commander of the 36th Division, had less confidence in the potential threat posed by his attack, confiding in his diary that he expected to fail. He certainly had a difficult task. His division had suffered badly at Salerno and again attacking San Pietro during the battle for the Bernhardt Line. Many of its officers and men were thus new to the division and inexperienced. The river itself was a formidable barrier, with its flood plain largely on the eastern, American held, side, and higher banks to the west. The Germans had also cut down all the cover on the eastern side of the river, so any American approach was in full view. The flood plain on the eastern bank had been flooded by the Germans, and the remaining patches of dry ground had been mined. None of the roads could take heavy traffic, so the assault troops had to carry their equipment, including all of the boats and related river crossing kit, across two miles of open ground under constant German artillery and mortar fire. The Germans had built a belt of dugouts, bunkers and trenches on the west bank, and had converted the ruins of the town of Sant Angelo into a fortress.
General Walker planned to make a two pronged assault, with two battalions from the 141st Infantry attacking north of Sant Angelo and two from the 143rd Infantry south of the town. Each attack force would be around 3,000 strong. The two forces were to advance past the town and meet up behind it. Combat engineers would accompany the assault force to deal with the German minefields on the east bank, mark out cleared routes, and build bridges over the river, which was deep and fast flowing but narrow.
The attack began at 8pm on 20 January under the cover of heavy fog. German artillery began to hit the attackers when they were still a mile east of the river, destroying boats and hiding the marked routes. The 141st lost one third of their boats and all four of the footbridges they were carrying.
Despite all of the heavy German fire, around 100 men from the 1st Battalion, 141st managed to get across the river, but they were then cut off, with their radios destroyed. At dawn the battalion commander ordered the attack to be suspended, and pulled back the troops still on the east bank.
To the south three platoons from the 1st Battalion of the 143rd got across. However they soon came under very heavy artillery fire after dawn, and the battalion commander, Major David M. Franzior, requested permission to retreat to avoid having his battalion annihilated. The retreat was completed by 10am, by which time both of the footbridges had been destroyed. The 3rd Battalion was unable to gain any foothold across the river.
For most of 21 January the only US troops across the river were thus the small party from the 141st. So far the attack had been a total failure, but the Anzio landings were about to begin, and Clark needed to keep the pressure up at Cassino. A new attack was thus launched late on 21 January.
On the left the 143rd managed to get three battalions across the river by 0200 on 22 January, but they were unable to build bridges to allow their supporting armour to cross. By the early afternoon it was clear that this crossing had failed, and the 143rd was ordered to retreat.
On the right the 2nd and 3rd Battalions of the 141st managed to get across the river, starting at 2100 on 21 January. However they found no sign of the survivors from the 1st Battalion, who had now been overrun. Work began on a bridge, but the engineers couldn’t work after dawn on 22 January because of the heavy and accurate German fire. Their footbridges were also destroyed, and the two battalions were pinned down within 600 yards of the river. By 6pm all but one officer had been wounded. After the 143rd retreated, the Germans were able to concentrate their efforts against the 141st, and only forty men managed to swim back to the relative safety of the east bank.
The assault across the Rapido had cost the 36th Division more than 2,000 casualties in 48 hours (155 dead, 1,052 wounded and 921 missing or captured) and had achieved nothing. The Germans hadn’t needed to move any fresh troops to the Rapido front, as the assaults never made enough progress to be threatening.