This was the US air attack on the monastery at Monte Cassino in the expectation that this would ease the task of the Allied ground forces in 'Avenger', otherwise the 2nd Battle of Cassino (15 February 1944).
In the 1st Battle of Cassino, the attention of a number of Allied commanders and commentators had come to be fixed on the great Benedictine abbey of Monte Cassino above the town of Cassino, and the idea that the Germans were using the abbey as an artillery observation point became increasingly accepted among these officers as the primary reason why the Allied forces were not able to break though the 'Gustav-Linie' defences in the area. The real reason for this failure was in fact the tactical ineptitude revealed in a succession of predictable and therefore costly frontal attacks on excellent defences held by determined and skilled troops.
The British press and C. L. Sulzberger of The New York Times often wrote of German observation posts and even artillery positions inside the abbey. At the headquarters of the New Zealand Corps it was thought that the abbey was probably in use as the Germans' primary artillery spotting position, largely on the grounds that the abbey was so ideally sited for such a role that no army could refrain from exploiting the capability. As Major General H. K. Kippenberger, commanding the New Zealand 2nd Division, wrote, 'If not occupied today, it might be tomorrow and it did not appear it would be difficult for the enemy to bring reserves into it during an attack or for troops to take shelter there if driven from positions outside. It was impossible to ask troops to storm a hill surmounted by an intact building such as this, capable of sheltering several hundred infantry in perfect security from shellfire and ready at the critical moment to emerge and counter-attack. Undamaged it was a perfect shelter but with its narrow windows and level profiles an unsatisfactory fighting position. Smashed by bombing it was a jagged heap of broken masonry and debris open to effective fire from guns, mortars and strafing planes as well as being a death trap if bombed again. On the whole I thought it would be more useful to the Germans if we left it unbombed.'
Major General F. I. S. Tuker, whose Indian 4th Division had been tasked with the attack on Monastery Hill, had come to his own conclusion after assessing the construction of the abbey: in a memorandum to Lieutenant General Sir Bernard Freyberg, commanding the New Zealand Corps, he wrote that whether or not the abbey was currently occupied by the Germans, it should be demolished to prevent its effective occupation, and also added that with walls 150 ft (46 m) high and at least 10 ft (3.1 m) thick, there was no practical way in which Allied engineers could breach the walls, and that an attack should therefore be made with 'blockbuster' bombs as conventional bombs up to a mass of 1,000 lb (454 kg) would be effectively useless. On 11 February 1944, Brigadier H. W. Dimoline, acting commander of the Indian 4th Division in the absence of Tuker, who was ill, asked for the abbey to be bombed, and was supported from his hospital bed by Tuker. On 12 February Freyberg passed the request up the chain of command to Lieutenant General Mark W. Clark, commanding the US 5th Army. Clark and his chief-of-staff, Major General Alfred Gruenther, were not at all convinced of the military necessity of bombing the abbey, and sought guidance from General the Hon. Sir Harold Alexander, commanding the Allied Central Mediterranean Force in Italy, who ordered the bombing to be undertaken.
The attack during the morning of 15 February involved 142 Boeing B-17 Flying Fortress heavy bombers, 47 North American B-25 Mitchell medium bombers and 40 Martin B-26 Marauder medium bombers of Lieutenant General Ira C. Eaker’s Mediterranean Allied Air Force command. These aircraft dropped 1,150 tons of HE and incendiary bombs on the abbey over a period of four hours. During the afternoon of the same day and on the following day heavy bombardments by the artillery of Major General Geoffrey T. Keyes’s US II Corps and air attacks by 59 fighter-bombers further shattered the rubble of the abbey. It seems probable that the only persons killed directly by the bombing were not German soldiers but some 230 Italian civilians who had taken refuge in the monastery.
It has been estimated that only 10% of the bombs from the heavy bombers, attacking from high altitude, actually hit the monastery. American bombs did fall right round the area of the monastery, killing both German and Allied troops as a byproduct of this misconceived undertaking. The size of the area unintentionally showered with bombs is revealed by the fact that so fewer than 16 bombs hit the 5th Army headquarters compound at Presenzano, some 17 miles (27 km) from Monte Cassino, and exploded only a short distance from the trailer in which Clark was working at his desk.
However, the initial air raid had not been co-ordinated between the air and ground commands, the timing having been decided by the USAAF on the basis of the attack being an operation separate from anything else and therefore scheduled in accordance with the weather and the requirements of other fronts and theatres. Thus the attack was delivered two days before the New Zealand Corps was ready to launch their main assault. In the context of the planned ground attack, therefore, the air attack achieved nothing.
On the day after the bombing, most of the civilians still alive fled the ruins, leaving only some 40 persons in the form of six monks, the abbot, the families of three tenant farmers, orphaned or abandoned children, and a number of badly wounded or dying men. After suffering artillery barrages, renewed bombing and attacks on the ridge by the Indian 4th Division, the monks decided to leave their ruined home with the others who could move at 07.30 in the morning on 17 February.
The bombing had turned the abbey in a shattered mass of ruins, which were ideally suited to defensive purposes, and in the circumstances the ruined abbey was now occupied by the paratroopers of Generalleutnant Richard Heidrich’s 1st Fallschirmjägerdivision of General Fridolin Ritter und Edler von Senger under Etterlin’s XIV Panzerkorps within Generaloberst Heinrich-Gottfried von Vietinghoff-Scheel’s 10th Army. The paratroopers swiftly turned the ruins into a superb fortress which checked every Allied effort to take it over the following three months.