Constans was succeeded by his son Constantine IV. after he had put down in Sicily a short-lived rebellion. He did not imitate his father’s violent deeds: he did not wish to maintain by force the Typus, which was still in legal existence. Pope Vitalian had done him service in his struggle with the usurper, and made use of his favourable sentiments to proceed with more decision against the Monothelites. The Monothelite patriarch Peter had died in 666, two years before Constans. The three following patriarchs, Thomas II., John V., and Constantine, inclined to orthodoxy. They occupied together only nine years, from 667 to 676. The Sixth Council left their names in the diptychs. Yet so great was the power which the Monothelites possessed in the capital that Constantine Pogonatus, though not a Monothelite, and much wishing to be reconciled with the Roman Church, thought it dangerous at the beginning of his government to alter the state of things; and the Typus, as law imposed by the State, was not abrogated. The next patriarch, Theodore, in 670 was again Monothelite, and he was, though moderate himself, induced by Makarius, patriarch of Antioch, to erase from the diptychs the names of all the Popes since Honorius. Pope Vitalian, after an admirable pontificate of fourteen years and a half, had died in 672, and was succeeded by the Roman, Adeodatus, who sat four years, and he by Pope Donus, also a Roman, in 676. Donus died in 678, and was followed by Agatho, a Sicilian of Palermo. During seven years, which end in 678, the Emperor Constantine was fighting a battle of life or death with the Saracen chalif Muawiah for Constantinople itself. Every year during several months the Saracen fleet was in the waters of the Bosphorus. They had taken the city of Cyzikus and wintered there, renewing the contest in the spring. During seven years they continued to do this. Had they taken the city the whole Christian empire in the East would have fallen. It is hard to limit the ruin which would have ensued to the Christian Church. But in weighing the events of this century the extreme peril in which the Church lay through the furious outburst of the Saracens should not be forgotten. On this occasion the Greek fire is said to have been first used. By it, as water would not extinguish it, many ships and their crews were destroyed. After this conflict of seven years, the Saracens having lost a great multitude of men, at last retired, owning that they were defeated. Their fleet in retiring met with a great tempest, and in a battle also which took place with three imperial commanders the Saracens lost 30,000 men. Muawiah, the chalif, treated for peace with the emperor, and it was concluded on glorious terms for the empire. This victory led the northern Avars also to treat the emperor with deference.(119)