300 men inside Tusculum. Other chroniclers claimed Christian had with him 1,000 cavalry and some Brabantine mercenaries. The lowest estimate of Christian's forces put it at 500 men. Christian encamped his army beside the hill and rested for a day while trying to negotiate a resolution. The communal Roman army refused Christian's diplomatic overtures and instead attacked with their whole force, numbering 10,000 poorly armed men, on Whitsunday. The name of the leader of the Roman force has not been preserved, but it may have been Oddo Frangipani. The Imperial forces were gravely outnumbered, but they were more disciplined and better armed. The Brabantines together with the cavalry from Rainald's city, Cologne, withstood the charge of the Roman infantry. Two sallies from Tusculum divided the Romans: one hitting their flank and one running through the centre. As the Roman cavalry fled the field, the Brabantines descended on the Roman camp. Only a third of the Roman army had made it inside Rome's walls before nightfall. Thousands were eventually taken prisoner and sent to Viterbo (including a son of Oddo Frangipani), and more were left dead on the field and the road. The pope and Oddo took refuge in the Colosseum (which at the time was fortified like a castle) and called in reinforcements. The city prepared for a siege. Later the pope fled to the city of Benevento and the Emperor entered Rome. The Imperial army, however, was hard hit by a wave of either malaria or plague, and Barbarossa withdrew his forces to Germany. Contemporary accounts A number of contemporary accounts of the battle exist, including a letter by Archbishop Rainald. This account of the battle by Otto of Saint Blasien is taken from the Monumenta Germanica Historica Scriptores SS., 20. In the year 1166 since the birth of Christ, Emperor Frederick, after settling the conflict between the princes, as we have mentioned, and restoring good order to the situation in Germany, assembled an army from all parts of the empire and led it into Italy, crossing the Alps for the fourth time. Then he crossed the Apennines, and, leading his army through Tuscany, he turned to the March of Ancona, and surrounded the rebellious city of Ancona with a siege. In the meantime, Reinald, the archbishop of Cologne, who had previously separated himself from the emperor on imperial business, turned against the castle of Tusculanum near Rome, as