Pope Pius XII personally wrote to President Franklin D. Roosevelt during the Second World War to beg him to spare Rome from bombing. A newly disclosed letter has unveiled the extent of the Vatican's anguish over Allied raids on the city and its cultural and architectural treasures.
In his letter, dated August 30, 1943, the wartime pope said Italy was "shackled and quite without the necessary means of defending herself."
The Pope continued: "We hope and pray that the military forces will find it possible to spare innocent civil populations, and in particular churches and religious institutions, the ravages of war.
"Already, we must recount with deep sorrow and regret, these figure very prominently among the ruins of Italy's most populous and important cities."
Pius, a controversial figure who has been criticised for failing to condemn the Germans when they rounded up Italian Jews, said he hoped that "God's temples and the homes erected by Christian charity for the poor and sick and abandoned members of Christ's flock, may survive the terrible onslaught."
The British and Americans began raids on Rome on May 16, 1943. One of the heaviest raids was on July 19, 1943, when more than 500 Allied aircraft bombed railway freight yards, steel factories and an airstrip, causing hundreds of civilian casualties.
During the air assault, tens of thousands of tons of bombs were dropped, for the loss of 600 aircraft and 3,600 aircrew.
Italy signed an armistice with the British and Americans in September 1943, after Mussolini was deposed from power.
But Rome was not liberated from the Germans until June, 1944, due to the fierce resistance around the beach heads of Salerno and Anzio and the mountain redoubt of Monte Cassino.
The letter has been kept for decades by the Knights of Columbus, a Catholic mutual aid society which was founded in Connecticut in 1882 and provided an important channel of information between Washington and the Vatican during the war.
It will go on public display in Rome's Capitoline Museums as part of an exhibition celebrating 90 years of friendship between the city and the Knights of Columbus.