The battle of Monte Porzio, 29 May 1167

The name of our town appears in one of the most important battles of medieval Rome. It was fought on 29 May 1167, Pentecost Sunday, at the foot of the hill of Monte Porzio, and for a moment it changed the balance between the emperor, the pope and Rome.

Where and when

The field was Prata Porci, the plain between the hill of Monte Porzio Catone and the walls of Tusculum, about 25 kilometres south east of Rome. The chronicles of the time place it “near Monte Porzio”. On the same plain, according to the reference entry on the Alban Hills volcano, there was an ancient volcanic basin.

Why it was fought

Behind it lies the struggle between Emperor Frederick Barbarossa, Pope Alexander III and the Commune of Rome. The Tusculans, that is the Counts of Tusculum, sided with the emperor against Rome, and at Prata Porci the imperial troops and the men of Tusculum found the Roman army in front of them.

Who fought

• For the empire: the archbishops Christian of Mainz and Rainald of Dassel, of Cologne, who led the troops. Barbarossa, according to the reference entry, was not there.
• For Rome: the name of the commander has not survived. It may have been Oddone Frangipane, but this is uncertain.
• At Tusculum: Count Raino, the emperor’s ally.

The numbers

The chronicles disagree, and so do historians today. The Romans were far more numerous: the usual figure is 10,000 men, poorly armed, though one chronicle goes as high as 30,000. The imperial side was small: about 1,300 or 1,600 depending on the source, including 500 knights and 800 imperial soldiers with Christian, plus 300 men inside Tusculum. Other chronicles speak of a thousand knights and Brabant mercenaries, and the lowest estimate is 500. The losses are not known.

How it went

The imperial side won. Only about a third of the Roman army managed to reach the walls of Rome by evening, and thousands of prisoners were sent to Viterbo, among them a son of Oddone Frangipane.

After the battle

Pope Alexander III and Oddone took refuge in the Colosseum, which was fortified at the time. Then the pope fled to Benevento and the emperor entered Rome. But Barbarossa’s army was struck by disease, malaria or plague depending on the source, and withdrew to Germany. One historian called the battle the “Cannae of the Middle Ages”, for the effect it had on Rome.

For the Tusculans the victory did not last. Count Raino, who had allied himself with the emperor, was refused entry to the city by his own people and was forced to sell his share of Tusculum to Alexander III, who already owned the other half. It marked the end of the main line of the family’s rule. Twenty four years later, in 1191, the Commune of Rome destroyed the city.

And Lake Regillus?

A much older battle was fought on these hills: the battle of Lake Regillus, which tradition places in 496 BC and which is covered in the article on Tusculum. The lake, which no longer exists, was near Frascati, but its exact position is uncertain.

A note on the sources

The English reference entry, which gives us many of the details, carries a notice that it needs more citations, and is based on medieval chronicles and on the historian Gregorovius. The oldest sources, such as Sicard of Cremona, speak of a clash “near Monte Porzio”.

In short

• When: 29 May 1167, Pentecost Sunday.
• Where: Prata Porci, between the hill of Monte Porzio Catone and Tusculum.
• Who: imperial troops and Tusculans against the Commune of Rome.
• Outcome: imperial victory; only a third of the Roman army got back to the walls that evening.
• Afterwards: Barbarossa in Rome, then the retreat; in 1191 Rome destroyed Tusculum.