midnight
A severe chastisement awaited their perfidy and inconstancy . Robert Guiscard was advancing with thirty thousand infantry and six thousand cavalry , and Henry fled before the redoubtable prince , whom he had provoked by an alliance with Alexis , the Emperor of the East . Abandoned by Henry , who had returned to Austria , the treacherous Romans barred their gates . Robert asked admission , but in vain ; and his irritated soldiers forced their way at midnight through the Flaminian gate . The city was crimsoned with flame and sword . A body of Saracens formed part of the Norman 's army , and their fury knew no bounds . From three points of the city the flames were streaming .