The Gustav Line was a staunch defensive line built by the Germans that spanned from the Tyrrhenian Sea to the Adriatic Sea. The Gustav Line ran along the Garigiliano and Rapido rivers on the west and on the Sangro river on the east side of the Italian peninsula. The line was defended by 15 German divisions fortified with small arms, artillery, pill boxes, machine gun emplacements, minefields and barbed wire. The German divisions had retreated to and fortified this line after the Allied invasion of Italy. In order to reach Rome, the "center of gravity" of the Italian resistance, the Allies had to push through this line to cut the communication lines of the German Army and open the way to Rome.
The Germans called the Gustav Line a "string of pearls anchored by Monte Cassino." Anchoring the Gustav Line, Monte Cassino was identified by the Germans and Allies as key terrain because of the outstanding observation it provided over the entrance to the Liri Valley. From Monte Cassino, one can see every road and river crossing at the mouth of the Liri Valley. Increasing the complexity of the Monte Cassino terrain was the Benedictine monastery built on top of it. The monastery, the source of the Benedictine Order of monks, was built around 529. The Rapido River formed part of the Gustav Line, acting as a natural moat, protecting Monte Cassino.
Because Great Britain looked upon the Mediterranean differently than the United States - it was after all a life-line of empire - its influence gradually predominated. America was more concerned with invading Western Europe and sought to limit its adventures in the Mediterranean. Before long-term Allied strategy could be agreed to, the British Eighth Army invaded Italy across the Straits of Messina. Regardless of intentions, once started the Italian campaign took on a life of its own.
The Allied landings in Italy in September 1943, followed quickly by the liberation of Naples and the crossing of the Volturno River in October, had tied down German forces in southern Italy. By year's end a reinforced German army of 23 divisions, consisting of 215,000 troops engaged in the south and 265,000 in reserve in the north, was conducting a slow withdrawal under pressure from the U.S. Fifth Army under Lt. Gen. Mark Clark and the Commonwealth and Allied forces of the British Eighth Army under General Sir Bernard L. Montgomery. The Allied operations in Italy between January and September 1944 were essentially an infantryman's war where the outcome was decided by countless bitterly fought small unit actions waged over some of Europe's most difficult terrain under some of the worst weather conditions found anywhere during World War II.
South of Rome the Germans constructed three major defensive lines: the Barbara Line, ill defined and improvised, stretching from Monte Massico to the village of Teano, to Presenzano, and to the Matese Mountains; the Bernhard, or Reinhard, Line, a wider belt of stronger fortifications forty miles north of Naples between Gaeta and Ortona, extending from the mouth of the Garigliano River near Mignano to Monte Camino, Monte la Difensa, Monte Maggiore, and Monte Sammucro; and the most formidable of the three belts, the Gustav Line, a system of sophisticated interlocking defenses, anchored on Monte Cassino, that stretched across the rugged, narrowest point of the peninsula along the Garigliano and Rapido Rivers.
In mid-January 1944 the Allied armies were through the first two belts and were facing the Gustav Line. Yet the Allied forces were exhausted from months of heavy fighting in bitter weather. The terrain also favored the defenders, who used the Apennine Mountains, with their deep valleys, foggy hollows, and rain-swollen streams and rivers, to slow the Allied advance to a crawl. Allied soldiers endured icy winds and torrential rains, lived in improvised shelters, ate cold rations, suffered from exposure and trench foot, and hauled their own munitions and supplies up and down steep mountainsides where vehicles and even mule trains were often unable to negotiate the few crude tracks or rocky crags. The Allies conducted repeated attempts to cross the Rapido River at different points on the river.
A plan was hatched in early December 1943 at Marrakech to make an amphibious landing (code named Shingle) at the port of Anzio-Nettuno, 80 miles north of the Gustav Line and 35 miles south of Rome. Several days prior to the invasion, a new offensive would be launched against the Gustav Line. The two fronts wereto be linked within seven days. In the early hours of January 22, 1944, the 1st Infantry Division and 3d Infantry Division landed at Anzio-Nettuno against minimal opposition. On the second day of the landing, knowing that the Allied attempt to breakthrough the Gustav Line two days earlier had failed, the Allies cautiously began to move inland. Two days after the landing more than 40,000 German troops faced the Allies. By the end of January the stage was set for what proved to be one of the bloodiest battles on the western front. By mid-February a quarter of a million men were locked in deadly combat on the Anzio plain. By early March the battle had been fought to a standstill; it became as static and deadly as the trenches of World War I. Not until the end of May did the renewed offensives in the south and at Anzio force the enemy to retreat from both fronts to positions north of Rome. Churchill's optimistic predictions proved to be wrong on every count.
The Allies had realized early in their campaign against the Gustav Line that the historic monastery dominating the summit of Monte Cassino (1,703 feet above sea level) was a crucial strategic point. Nevertheless, they exempted the monastery, founded in 524 A.D. by St. Benedict, from air, artillery, and ground attacks during the American assaults on Cassino. Even though the Allies later learned that the monastery itself was never permanently occupied by the Germans, frequent sightings of enemy personnel within its walls raised suspicions. In addition, the enemy built heavily fortified emplacements and observation posts within feet of the monastery to take full advantage of the terrain and Allied firing prohibitions.
Some Allied aerial observes and ground forces stated they saw German soldiers, including snipers and artillery spotters, inside the ancient building. The German commander insisted his forces were in the area around the monastery, but not inside it. History proves the German commander was being truthful. The official U.S. position on the Monte Cassino bombing underwent several changes. The statement "irrefutable evidence" concerning the German use of the abbey was removed from the official record in 1961 by the Office of the Chief of Military History. In 1964 the record was changed again to, "It appears that no German troops, except small military police detachment, were actually inside the abbey before the bombing. The final correction to the official record came five years later. In 1969 the official account was changed to read, 'The abbey was unoccupied by German troops.'
At the time there was no consensus that the Allied exemption regarding Monte Cassino was wise. General Alexander and his superiors had long maintained that the safety of such areas would not be allowed to interfere with military necessity. When General Freyberg began to plan his assault, he concluded that the monastery would have to be reduced and requested air attacks.
The Americans sought to use the opportunity to showcase the abilities of the U.S. Army air power to support ground operations. Following the dropping of leaflets warning civilians in the monastery to evacuate, the Tactical and Strategic Army Air Forces, consisting of the 319th, 340th, 321st, 2d, 97th, 99th, and 301st Bomber Groups, began their bomb runs at 0945, 15 February 1944. A total of 142 B-17s, 47 B-25s, and 40 B-26s dropped 1,150 tons of high explosives and incendiary bombs on the abbey, reducing the entire top of Monte Cassino to a smoking mass of rubble. The controversial bombing destroyed much of the monastery and its outer walls but did not penetrate the subterranean chambers the Allies thought the Germans were using as bomb shelters. When the 4th Indian Division launched its attack on the night of 15 February, it was repulsed with heavy casualties. Over the next three days fighter-bombers provided close support of further Indian assaults, all of which failed with tremendous losses.
In mid-March 1944 the Allies attacked Monte Cassino again. Although most commanders now doubted whether air assaults could reduce the Cassino defenses to the point where the infantry could succeed, a large air attack was nonetheless planned. Successive waves of bombers were to pulverize Cassino between 0830 and noon, delivering 750 tons of 1,000-pound bombs with delayed-action fuses.
On 15 March 1944, Generals Clark, Alexander, Eaker, Freyberg, and Devers watched the air attack on Cassino from three miles away. On schedule, 514 medium and heavy bombers, supported by 300 fighter-bombers and 280 fighters, dropped high explosives on the area. The bombardment failed to meet expectations. As the infantry and armored units advanced over the cratered and now nearly impassable terrain, they found the German positions still intact and enthusiastically defended. Despite new air attacks by fighter-bombers, and another 106 tons of bombs, the New Zealanders and Indians made little progress. Still further air attacks on 16-17 March, which dropped 466 tons of bombs, produced no tangible results. By 21 March, seven days into the attack, General Clark called on Freyberg to break off the assault, a decision thought prudent by Generals Juin and Leese as well. Yet thinking that success was just within reach, Freyberg continued the attack until Alexander compelled him to halt the offensive on 23 March. After multiple air assaults, the firing of 600,000 artillery shells, and 1,316 New Zealander and 3,000 Indian casualties, Cassino, Monte Cassino, and the Liri valley remained in German hands.
In an effort to break the German defenses (and minimize casualties), the American air forces began operation "Strangle" in March 1944. Designed to stop the flow of supplies to the Germans, it focused on railroads and roads well north of Rome. In the first week, the Allies cut every railroad in at least two places. Thereafter, they averaged 25 cuts per day. Rail capacity fell from 80,000 tons per day to 4,000, well below what the Germans needed to resist an intensive offense. On 4,000 tons a day, however, the Germans could survive in the absence of Allied ground attack. Thus, they did not withdraw.
The Allies had failed to break the Gustav Line three times: in January with the ill-fated assaults on the Rapido River; in February with the attempt to outflank Cassino; and in March with the attempt to drive between the monastery on Monte Cassino and the town below. The Germans remained in firm control of the fortified line stretching from the Gulf of Gaeta on the Tyrrhenian Sea to the Adriatic, and they were now preparing the Hitler Line, five to ten miles farther north. These new defenses stretched from Terracina to the Liri valley and Monte Cairo and were manned by the equivalent of nine divisions of the L1 Mountain Corps under Lt. Gen. Valentin Feuerstein. To meet further Allied attacks, the Tenth and Fourteenth Armies gathered 365,000 soldiers, the bulk of the 412,000 German troops stationed in Italy south of the Alps.
General Alexander used the period from March to May 1944 to rebuild his forces and plan the final push on Rome. To assure an overwhelming victory, and to avoid the battles of attrition encountered thus far, the 15th Army Group commander estimated that he needed at least a three-to-one advantage in infantry over his adversaries, requiring a major reorganization of the Allied line. The Fifth Army front was therefore reduced to twelve miles - just the narrow coastal plain along the Tyrrhenian Sea. The long-awaited spring offensive commenced on 11 May 1944. The Polish Corps assault on Monte Cassino failed with more than 50 percent of the attacking force counted as casualties.
Having lost over 40 percent of their combat strength in just three days, with pressure building along the entire Gustav Line, and faced with the encirclement of Cassino, the Germans began to withdraw to the north, fighting desperate rearguard actions the entire way. What made an enormous difference, however, was the German inability to move reserves to the front or to move forces laterally along it. The interdiction campaign had taken such a toll of trucks and trains, and had done so much damage to bridges, railroads, and roads, that the Germans were dependent on foot power and animal transport to move anywhere.
By the early morning hours of 16 May, the American II Corps and French Expeditionary Corps (FEC) had broken the Gustav Line. The German commander Kesselring was forced on 2 June to order all German units to break off contact and withdraw north, declaring Rome an open city on 3 June.
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