On 23 March 1944, a column of the German 11th Company, 3rd Battalion, SS Police Regiment 'Bozen', was attacked by an ambush of Partisans while marching and singing on a prescribed route that led through the Piazza di Spagna into the narrow street of Via Rasella. Organized by the Nazis to intimidate and suppress the Resistance, the battalion had been raised in October 1943 from ethnic German-speakers of the northern Italian province of South Tyrol, a territory that Hitler had annexed to the German Reich after the September "betrayal" by the Italian government. Many of its citizens had since opted for German citizenship. The soldiers of the battalion were veterans of the Italian Army who had seen action on the Russian Front and had chosen service in the SS rather than face another tour in the East with the Wehrmacht.
The attack was carried out by 16 partisans of the Communist-dominated resistance organisation Gruppo d'Azione Patriottica ("Patriotic Action Group") or GAP. An improvised explosive device was prepared consisting of 12 kilograms of TNT packed in a steel case. This was inserted into a bag containing an additional six kilograms of TNT and TNT filled iron tubing. Although reported as having been thrown from a building, the bomb had actually been hidden in a rubbish cart, pushed into position by a Partisan disguised as a street cleaner, while others acted as lookouts. The fuse was lit when the police were forty seconds from the bomb. The blast caused the immediate deaths of 28 SS policemen and at least two civilian bystanders, one of whom, Piero Zuccheretti, was an eleven-year old boy. More would die over the next few days.
All sixteen Partisans — some of whom fired on the German column — succeeded in melting away into the crowd unscathed.
The German police attaché and commander of the Security Police in Rome, SS Obersturmbannführer Herbert Kappler was on the scene soon afterwards to supervise the investigation. That evening he was summoned to the headquarters of the German Armed Forces Commandant in Rome, Luftwaffe Generalmajor Kurt Mälzer, who had decided that the killings called for reprisals.
They agreed that the execution of ten Italians for each German policeman killed was a suitable ratio. Mälzer, who also proposed burning down part of Rome, passed this on to General Eberhard von Mackensen, the commander of the Fourteenth Army, whose jurisdiction included Rome. General Mackensen endorsed the recommendation. In turn, the staff of the German Commander-in-Chief South (Oberbefehlshaber Süd), passed this on to the Oberkommando der Wehrmacht (OKW). That night, Adolf Hitler authorized the reprisal, stipulating that it be carried out within 24 hours. Commander-in-Chief South Generalfeldmarschall Albert Kesselring, considered this an order, one he interpreted as calling for the execution of Italians who had been previously sentenced to death. He was reassured by Kappler that sufficient prisoners were available.
However, Kappler had only four prisoners sentenced to death in his Hausgefängnis (private prison) at SS headquarters in the German Embassy on 145 Via Tasso; plus 17 serving long sentences; 167 deemed "worthy of death"; and two to four civilians who had been rounded up in the Via Rasella area on suspicion of involvement in the Partisan attack. Kappler's superior, SS Brigadeführer und Generalmajor der Polizei Dr. Wilhelm Harster, suggested making up the numbers from the 57 Jews also in Nazi custody. By noon on 24 March, Kappler had a list of 271 victims, each with his crime listed against his name, except for the Jews, simply listed as "Jew". But by this time the death toll of the Via Rasella bombing had risen to 32. (One more would die while the reprisal was under way; the death toll eventually reaching 42.) To make up the numbers, Questore Pietro Caruso chief of the Fascist police in Rome, offered some Italians from his Regina Coeli prison, one of whom, Maurizio Giglio, had been his own Lieutenant, before being unmasked as a double agent working for the American OSS in charge of radio communications with the Fifth Army. Because of the time limit that Hitler had imposed, Mälzer and Kappler agreed that the victims would have to be shot in the back of the head at close range rather than by conventional firing squad.[
The massacre was perpetrated without prior public notice in what was then a little-frequented rural suburb of the city, inside the tunnels of the disused quarries of pozzolana, near the Via Ardeatina. By mistake, a total of 335 Italian prisoners were taken, five in excess of the 330 called for. On 24 March, led by SS officers Erich Priebke and Karl Hass, they were transported to the Ardeatine caves in truckloads and then, in groups of five, put to death inside the caves.
Because the killing squad mostly consisted of officers who had never killed before, Kappler had ordered several cases of cognac delivered to the caves to calm their nerves. The officers were ordered to lead the doomed prisoners into the caves with their hands tied behind their backs and then have them kneel down so that the soldiers could place a bullet directly into the cerebellum, ensuring that no more than one bullet would be needed per prisoner.
Many were forced to kneel down over the bodies of those who had been killed before them because the cave had become filled with dead bodies. During the killings, the existence of the five extra prisoners was discovered, and it was decided to kill them anyway, in order to prevent news of the location of the place of execution from becoming known. Some of the German officers involved in the massacre were horrified by the slaughter. One, who refused to shoot, was personally dragged to the execution site by Erich Priebke, who put his arm around the officer's waist and forced him to kill his victim.
Another, named Amon, testified at the trial of Kappler which was held in Italy in 1948; saying that once he entered the cave and saw the piles of dead bodies, he fainted and was replaced by a comrade who pushed him aside and shot another victim.
The massacre took most of the day and soon degenerated into a drunken shambles. Some of the victims' heads were blown off by the shots; others were only wounded and may have survived until the explosions intended to seal the caves after the massacre was completed: one youth and his father were found in each other's arms in a corner of the cave galleries which had not been filled with the debris under which most victims had been buried. Some crawled into corners to die.
The bodies of the victims were placed in piles, typically about a meter in height, and then buried under tons of rock debris when German military engineers set explosives to seal the caves and hide the atrocity. They remained summarily buried and abandoned for over a year inside the caves. Families of the victims were notified with excruciating slowness by individual letter, if at all, a strategy of coverup and concealment – "Night and Fog" – designed to confuse, grieve, and intimidate surviving relatives, according to Robert Katz. Only after the Italian capital was liberated by the Allies on 4 June 1944, were the bodies finally found, by Armando Della Valle and another fireman who were sent to search in the caves after a tip off, exhumed, and at last given proper burial. The scale and even the occurrence of this retaliation was unprecedented on Italian soil.
Misconceptions about the Fosse Ardeatine Massacre abound.
Foremost among these is the notion that the Partisans responsible for the Via Rasella attack were ordered to come forward and turn themselves in to the SS and wilfully declined to do so. This stems from a fallacious belief (still cultivated by neo-fascist claims, despite their refutation by Alessandro Portelli) that the Nazis warned the Roman populace that a retaliation was imminent. The concept of "ten Italians for one German" is also frequently cited in making this argument, implying that the Partisans could or should have realized beforehand that their attack would cost 330 innocent Italians their lives. In fact, in the hours following the bombing, there were arguments among the Nazi leadership in Rome as well as between Hitler and his commanders as to whether 10, 30, or 50 Italians should be killed for every dead German, not to mention whether all or part of the city of Rome should also be burned. As noted above, however, the first public news of both the bombing and the reprisal came at noon on the day after the attack, when the Germans issued an announcement, blaming "Badoglio-Communists" for the "crime" and spelling out for the first time the terms of the reprisal, with the chilling words at the end: "The order has already been carried out".
Although it is sometimes claimed that the reprisal victims were predominantly Jewish, only 75 of the 335 victims selected for death in the caves were Jewish, this having been a criterion for selection (because Jews were known to be marked for death anyway). In fact, the victims comprised, in Robert Katz's words, "rich, and poor, doctors and lawyers, workers and shopkeepers, artists and artisans, teachers and students, men and teenaged boys from every walk of life, and even a man of God to walk among them". The main concern of the SS had been speedy fulfillment of the quota. Some were residents of Via Rasella who were home at the time of the Partisan attack; others had been arrested and tortured for suspected Resistance and other anti-Fascist activities, while still others had been casually picked up on the streets or arrested at their homes on the basis of tips from fascist informants. The youngest of them was 15 years old.
Political prisoners included members of the GAP, the PA, and the Monarchist Clandestine Military Front of the Resistance (FMRC), which included many policemen. Members of the Bandiera Rossa ("Red Flag") a dissident communist Resistance group, constituted the largest group. One political prisoner, Padre Pietro Pappagallo, was one of the models for the character of Padre Pietro in Roberto Rossellini's pioneering neo-realist film Rome, Open City, filmed in 1944. Another, perhaps the most celebrated, was the aristocratic Colonel Giuseppe Montezemolo (age 44), who, after the flight of the King and Badoglio, had elected to stay and go underground in Rome, disguised in mufti as a professor or Ingegnere (engineer), to organize and lead the FMRC, representing the Badoglio Government, with which he had been in continual radio contact up until his arrest on 25 January 1944.