The 'Battle of Cisterna' was fought between US and German forces within the context of the Battle of Anzio following the 'Shingle' landings (30 January/2 February 1944).

The battle was a comparatively small but clear German victory which had repercussions locally and on a wider scale on the employment of US Army Ranger forces that went beyond the immediate tactical and operational results of the battle.

During this battle, the 1^st, 3^rd, and 4^th Ranger Battalions, the 83^rd Chemical Mortar Battalion, and the 509^th Parachute Infantry, which had been brigaded as the 6615^th Ranger Force (Provisional) commanded by Colonel William O. Darby, were assigned to support the renewal of an attack by Major General Lucian K. Truscott’s US 3^rd Division of Major General John P. Lucas’s US VI Corps within Lieutenant General Mark W. Clark’s US 5^th Army, which had previously failed to take Cisterna between 25 and 27 January. The 3^rd Division’s attack was part of a major attack the VI Corps to break out of the Anzio beach-head before German reinforcements could arrive and concentrate for a counterattack.

It was on 22 January that the Allies had launched 'Shingle' as an amphibious assault by the US and British divisions of the VI Corps in the area of Anzio and Nettuno on the south central coast of western Italy. The operation had been designed as the means of unhingeing the formidable German defences of the 'Gustav-Linie', some 60 miles (100 km) to the south-east, which had been under attack, as yet unsuccessfully, from the south by the other three corps (one British, one Free French and one US) of the 5^th Army since 16 January in the 1^st Battle of Monte Cassino. Following the 'Shingle' landings, which took place almost without opposition, Lucas had opted for a cautious strategy based on the consolidation of the beach-head and the increase of his corps' strength. This essentially passive stance gave the Germans the opportunity to reinforce their defensive positions. By 29 January, therefore, there were 69,000 Allied troops in the beach-head, but the Germans had also had time to react and move 71,500 troops, under command of Generaloberst Eberhard von Mackensen’s 14^th Army, to face them.

On 31 January, Lucas launched a two-pronged attack. The main attack, by Major General W. R. C. Penney’s British 1^st Division, was to advance from the north-western edge of the beach-head in a north-easterly direction up the Via Anziate toward Campoleone and the Alban hills. In a simultaneous but secondary attack, a Ranger force was to advance from the south-east edge of the breach-head in a northerly direction to infiltrate Cisterna and clear the road linking Conca and Cisterna during the night in preparation for an attack in the morning by the US 15^th Infantry on the town and supporting attacks by the 504^th Parachute Infantry and the 7^th Infantry on its right and left respectively. The 7^th Infantry was to cut Route 7, the main supply line to Generaloberst Gottfried von Vietinghoff-Scheel’s German 10^th Army at Cassino on the 'Gustav-Linie'.

The Allied plan was flawed, however, as it was based on misinterpretation of reconnaissance intelligence, which had concluded that the main line of German resistance was behind Cisterna whereas, in fact, the Germans had designated Cisterna as an assembly area for its reserve divisions and had begun moving formations and units into the area. Although a Polish conscript in the German army had deserted to the US lines immediately before the attack and warned of the German build-up, the information was not relayed promptly and the attack proceeded as planned. The Rangers, who expected to encounter a line of thinly-held outposts, thus advanced unknowingly toward a large German force.

Contrary to their designated function as an elite raiding force, the Rangers had already been involved in much of the front line fighting around the Anzio beach-head. The Rangers' casualties meant the introduction into their ranks of many replacements, mostly recruits who lacked the experience and quality of training of the original members. The growing presence of green troops in an otherwise skilled force degraded its ability to undertake both a successful infiltration and night operations.

The 1^st and 3^rd Ranger Battalions, preceding the main attack by the 4^th Ranger Battalion and the 3/15^th Infantry, attempted a night infiltration into the area behind the German lines and into Cisterna. The Rangers' objective was to seize the town in a surprise attack and hold it until the arrival of the main attack.

Totaling 767 men and supported by a 43-man platoon of the 3^rd Reconnaissance Troop, the two Ranger battalions moved out at 01.30 and in the darkness moved along a drainage ditch (the 'Mussolini Canal') in column formation. Although they were able to bypass numerous German positions, at first light the Rangers were still short of their objective and needed to cross open ground for the last part of their approach. At this point the Rangers came under attack by a strong Germans force of were attacked by strong German forces of Generalleutnant Hans-Georg Hildebrandt’s 715^th Division of General Traugott Herr’s LXXVI Panzerkorps and Generalmajor Paul Conrath’s Panzerdivision 'Hermann Göring', the latter including at least 17 PzKpfw IV battle tanks. It is believed that the Ranger’s infiltration had been discovered and the Germans had laid an ambush.

The commander of the 1^st Ranger Battalion, Major Dobson, knocked out one of the tanks by shooting the commander with his pistol, climbing onto the vehicle and dropping a white phosphorus grenade down the hatch. Two other tanks were captured by Rangers but then knocked out by other Rangers ignorant of the fact that they had been captured. Despite fierce fighting, there was little chance of success once the lightly armed Rangers had come under attack on open ground. German units put Ranger prisoners in front of their tanks and ordered the other Rangers to surrender. The German took prisoner more than 700 men.

The main assault also jumped off, but its task was now to attempt the rescue of the trapped battalions. Spearheaded by the 4^th Ranger Battalion, the main attack encountered serious opposition and failed to break through. However, the overall assault, which also included an attack by the 7^th Infantry and 504^th Parachute Infantry, did manage to push the Allied perimeter forward some 3 miles (4.8 km) on a front 7 miles (11.25 km) wide on 31 January and 1 February. But the main attack failed to achieve the desired breakthrough, and Cisterna was to remain in German hands until the US force’s 'Buffalo' offensive out of the Anzio lodgement late in May 1944. However, the German 'Fischfang' counterattacks on 1 and 2 February by the Panzerdivision 'Hermann Göring' and Generalmajor Fritz Roske’s 71^st Division failed to retake any of the ground from the Allies and suffered severe casualties.

Later intelligence revealed that the US efforts had helped to disrupt the Germans' planned 'Fischfang' counterattack of 3/4 February on the Allied beach-head.

Lucas came under severe criticism for his decision to make use of the lightly armed Rangers to spearhead the attack. As a result of the 'Battle of Cisterna', the battered Ranger forces in Italy were subsequently disbanded, and as many as 400 of them served as replacements in the US/Canadian 1^st Special Service Force, an elite raiding force in need of high-quality replacements.

Darby had commanded the Ranger Force during the battle and when, on 18 February, the 179^th Infantry of Major General William W. Eagles’s 45^th Division was nearly overrun in 'Sonnenaufgang' launched by the Germans to destroy the Allied lodgement, Darby was sent to take command and hold the ground.