On 19th July 1943, between 11 a.m. and 12 noon, 150 Allied B-17 bombers attacked a freight yard and steel factory in Rome near the Basilica di San Lorenzo fuori le Mura [Saint Lawrence Outside The Walls]. During the attack bombs fell upon the Basilica causing major damage and killing and injuring more than one thousand civilians.

Pope Pius XII had been deeply concerned about the threat war posed to Rome and the likelihood Rome might be a major target. The Allied forces first bombed Rome on 16th of May 1943, leading the Pope to ask US President Franklin Roosevelt that Rome “be spared as far as possible further pain and devastation, and their many treasured shrines… from irreparable ruin.” Roosevelt promised that Allied planes were instructed to avoid bombing Vatican City and that neither civilian nor non-military sites wold be targeted. The US command wanted to pay particular attention to preserving the safety of Catholic places because of the large number of Catholics in the US Armed Forces.

The Allied bombers had not intended to damage the basilica. Indeed, the Allied commanders had specifically ordered in regards to the Vatican, the Basilica of Saint John Lateran and the Basilica of Saint Paul Outside the Walls that they “must on no account be damaged.” Before the bombing, Allied planes dropped leaflets explaining that no attempt was being made to bomb “those cultural monuments which are the glory not only of Rome but of the civilized world.” However, some of the Allied bombs fell short of their intended targets and struck San Lorenzo.

Immediately after the bombing of the Basilica di San Lorenzo, Pius XII and Msgr. Giovanni Batista Montini [the future Paul VI] went to the basilica and distributed ₤ 2 million to the victims. Those who were there on that day would remember how the white cassock of the Pope would be stained red with the blood of the victims.

On 20 July 1943, Pius XII sent an angry message to President Roosevelt in which he said, “As Bishop of this Sacred city we have constantly tried to save our beloved Rome from devastation…But this reasonable hope has, alas, been frustrated.” Several US Bishops sympathized with this response.

However, some US Bishops, such as Bishop Joseph Lynch of Dallas and Edwin O’Hara of Kansas City, defended the bombing on the grounds that the Basilica had not been deliberately targeted and that such attacks were necessary to overcome the evil of the Axis powers. American Catholics would also blame Mussolini for not declaring Rome an open city which would have protected it from Allied attack.

The Basilica di San Lorenzo would be restored in 1948. During the restoration many of the changes to the church which were made during Pius IX’s 19th century restoration were removed.

E il Papa la domenica mattina da San Pietro,
uscì tutto da solo tra la gente, e in mezzo a San Lorenzo,
spalancò le ali, sembrava proprio un angelo con gli occhiali.
[And the Pope that Sunday morning at San Pietro,
went out alone among the people, and in the middle of San Lorenzo
he spread his wings, he looked like an angel with glasses.]
Francesco De Gregori – San Lorenzo

A very interesting collection of photos of the Basilica di San Lorenzo and how it looked before the bombing, after the bombing and how it looks today
An image of Pius XII at San Lorenzo after the bombing