Revolt and Extraordinary Death of Procopius. Eleusius, Bishop of Cyzicus, and Eunomius, the Heretic. Eunomius succeeds Eleusius
It is probable that a severe persecution might have ensued at this juncture, had not Procopius commenced a civil war. As he began to play the tyrant at Constantinople, he soon collected a large army, and marched against Valens.
The latter quitted Syria, and met Procopius near Nacolia, a city of Phrygia, and captured him alive through the treachery of Agelon and Gomarius, two of his generals.
Valens put him and his betrayers to a cruel death; and although it is said that he had sworn to show favor to the two generals, he caused them to be sawn asunder.
He commanded Procopius to be fastened by the legs to two trees which had been bent to the ground, and he allowed these to spring up; when the trees were left to resume their natural position, the victim was torn in two.
On the termination of this war, Valens retired to Nicæa, and finding himself in possession of profound tranquillity, he again began to molest those who differed from him in opinion concerning the Divine nature.
His anger was unbounded against the bishops of the council of Lampsacus, because they had condemned the Arian bishops and the formulary of faith set forth at Ariminum.
While under the influence of these resentful feelings, he summoned Eleusius from Syria, and having called together a Synod of bishops who held his own sentiments, he endeavored to compel him to assent to their doctrines. Eleusius at first manfully refused compliance. But afterwards, from the dread of exile and deprivation of his property, as was threatened by the emperor, he yielded to the mandate. He soon repented of his weakness, and on his return to Cyzicus he made a public confession of his fault in the church, and urged the people to choose another bishop, for he said that he could not discharge the duties of a priesthood after having been a traitor to his own doctrine. The citizens respected his conduct and were especially well-disposed to him, so that they did not choose to have another bishop. Eudoxius, president of the Arians in Constantinople, however, ordained Eunomius as bishop of Cyzicus; for he expected that by his great powers of eloquence Eunomius would easily draw the people of Cyzicus over to his own sentiments. On his arrival at that city he expelled Eleusius, for he was furnished with an imperial edict to that effect, and took possession of the churches himself.
The followers of Eleusius built a house of prayer without the walls of the city, and here they held their assemblies. I shall soon again have occasion to revert to Eunomius and the heresy which bears his name.
Source: Ecclesiastical History (New Advent)