Battle of San Pietro Infine

The Battle of San Pietro Infine (commonly referred to as the "Battle of San Pietro") was a major engagement from 8–17 December 1943, in the Italian Campaign of World War II involving Allied Forces attacking from the south against heavily fortified positions of the German "Winter Line" in and around the town of San Pietro Infine, just south of Monte Cassino about halfway between Naples and Rome. The eventual Allied victory in the battle was crucial in the ultimate drive to the north to liberate Rome. The battle is also remembered as the first in which the troops of the Italian Royal Army (Regio Esercito) fought as co-belligerents of the Allies following the armistice with Italy. The original town of San Pietro Infine was destroyed in the battle; the modern, rebuilt town of the same name is located a few hundred meters away.

North Africa and Sicily
The Allied invasion of Italy from the south followed the Allied successes in North Africa. Eighth Army's advance from the east following the Second Battle of El Alamein and the British-American invasion of French North Africa by the British First Army in Operation Torch had led by May 1943 to the surrender of Axis forces in Africa.

The Germans retreated to the island of Sicily and on the night of 9/10 July 1943, an Allied armada of 2,590 vessels launched one of the largest combined operations of World War II: the invasion of Sicily. Over the next five weeks, 500,000 Allied soldiers, sailors, and airmen fought German and Italian forces for control of the island. Although the Allied powers were victorious, the Axis managed to evacuate over 100,000 men and 10,000 vehicles from Sicily across the Straits of Messina during the first seventeen days in August. The Allies then invaded the Italian mainland in September 1943 at Salerno, in Calabria (Operation Baytown) and Taranto (Operation Slapstick).

On 8 September, before the main invasion, the surrender of Italy to the Allies was announced. Italian units ceased combat, and the Italian Navy sailed to Allied ports to surrender. This changed the German defensive strategy greatly, and the Germans now regarded their former allies as enemies and moved to disarm Italian units and occupy important defensive positions. The invasion at Salerno was ultimately successful and Allied forces took nearby Naples on 1 October. German forces then withdrew to the north toward Rome and dug in along a series of well-fortified lines. By late 1943 fighting had reached the Winter Line.

Italy


The German commander—General Albert Kesselring—had marked out the "Winter Line" as three parallel defensive systems to the south of Rome. The defensives lines were called the Reinhard Line, Gustav Line and Hitler Line, placed 18 km one from the other, taking advantage of the point at which the Italian Peninsula is narrowest; they served as a formidable series of obstacles in the path of the Allied march toward Rome. The Reinhard was the southernmost of the three and was the German fall-back position from the Barbara Line and Volturno Line further to the south as German forces retreated gradually up the peninsula. (The Reinhard was also called the Bernhardt Line.) The Reinhard was actually a southern bulge in the stronger Gustav line to the north. On the eastern side, the Reinhard went from the Sangro River to the Adriatic Sea (along which length it was identical to the Gustav Line); then, in the west, it bulged south from Cassino to incorporate the mountains overlooking the approaches to the Liri Valley and then moved west to the mouth of the Garigliano River. The line passed directly through the town of San Pietro Infine, blocking the Mignano Gap, the pass through which Route 6, the main road up the center of Italy from Naples to Rome, ran toward Cassino and the entrance to the Liri valley.

Preparations


The Germans occupied San Pietro in September 1943 to prepare the defenses. They evacuated all non-essential Italians from the town, meaning women, children and old men; they conscripted able-bodied men to help set up the defenses and requisitioned available vehicles and beasts of burden. They set up a defensive apparatus in the whole territory, in particular on Mount Sambúcaro and Mount Lungo, which overlooked the Mignano Gap. These were strategically important positions because they allowed the control of the long stretch of Route 6, important for the advance of the Allies. The Fifth Army began to attack the Reinhard/Bernhardt Line on 5 November, and the attacks continued into December.

The Battle of San Pietro was preceded by Allied attacks on the Camino hill mass at the entrance to the Mignano Gap (named for the small town on the road at that point). The entire hill mass is about 10 km long and 6 km wide. After that, the main Allied effort was against the German defenses on Mount Sambùcaro and Mount Lungo, which dominated the narrow valley on the east and west respectively. As a point of historical interest, the assault on Mount Lungo was aided for the first time by the 1st Italian Motorized Group, part of the recently reconstituted Italian army, now fighting on the side of the Allies.

The battle


The direct attack on the German positions in and around San Pietro began on 8 December by II Corps of the Fifth Army. The positions were defended by the second and third battalions of the 15th Panzer Grenadier Regiment and the second battalion of the 71st Panzer Grenadier Regiment, all part of German Tenth Army's XIV Panzer Corps.

After a week of intense attacks and counter-attacks, the U.S. 36th Division's 143rd Infantry Regiment and the 82nd Airborne Division's 504th Parachute Infantry Regiment commanded the heights of the Sambùcaro mass. The U.S. 36th Division, then planned a further effort for 15 December. 143rd Infantry assisted by 504th PIR would continue to push west along the shoulders of Sambùcaro and take San Vittore del Lazio while to the south of Route 6 142nd Infantry Regiment supported by the Italian 1st Motorized Group were to capture Mount Lungo. In the center, 141st Infantry would attack San Pietro itself. The main attack of the 36th Division started at 12:00 on 15 December. In an effort to break the German defenses in the town, two platoons from the 753rd Tank Battalion attacked with 16 Sherman Tank and Tank Destroyers. The armored attack failed due to mines and anti-tank fire. Four of the 16 tanks survived. After four successive Allied attacks and German counter-attacks, the Germans pulled back from San Pietro since the dominating ground on both flanks, Mount Lungo and the Sambùcaro peaks, was now in II Corps' possession. The Germans launched a counter-attack on 16 December to cover their withdrawal as they retreated to positions farther north at Cedro Hill, Mount Porchia, San Vittore, and the western spurs of Sambúcaro.

Aftermath
The Battle of San Pietro was part of the overall campaign to breach the Bernhardt/Reinhard Line, some 10 km deep at that point. It took six weeks of heavy fighting—from early November to late December—to overcome the German defenses. During that time, the Fifth Army sustained 16,000 casualties. The highway through the Mignano Gap to the Liri Valley was nicknamed "Death Valley" by members of the attacking force. The battle destroyed the town of San Pietro Infine completely. Destruction was wrought by a combination of close combat, both Allied and German mortar and artillery, and German "scorched earth" policy. Both the battle and the plight of the civilian population have inspired numerous accounts, most famous of which is the John Huston film The Battle of San Pietro.

By mid-January, Fifth Army had reached the formidable Gustav Line defenses and commenced the first Battle of Monte Cassino, which started on 17 January 1944.