[3][4] Thoros (together with his father, Leo I and his brother, Roupen) was kidnapped in 1137 by the Byzantine Emperor John II Comnenus during his campaign against Cilicia and the Principality of Antioch.
[6] Thoros was of a tall figure and of a strong mind: his compassion was universal; like the light of the sun he shone by his good works, and flourished by his faith; he was the shield of truth and the crown of righteousness; he was well versed in the Holy Scriptures and in the profane sciences.
[8] Leo I took refuge in the Taurus Mountains, but at last found the situation hopeless, and surrendered himself to the conqueror;[5] Thoros was kidnapped with his father and his youngest brother, Roupen.
Before the end of the year /1141/ the emperor left Constantinople with a large army, and went to assist the Prince of Antioch, who was hard pressed by the Turks.
Being on a hunting party in the valley of Anazarbus, one of his own poisoned arrows wounded him, and he fell dead on the spot; he thus met with his deserved fate (…) The Greek army returned, but Thoros remained in the country; though the traditions concerning this fact are different.
Some say, Thoros withdrew himself quite alone, went by sea from Antioch to Cilicia, and took possession of his dominions, finding means to gain at first the town of Amouda, and afterwards all the other places.
There were many Armenians in this part of the country who, being barbarously treated by the Greeks, sighed for their former masters; to these men, as it is said, the priest imparted the joyful tidings; they instantly assembled and appointed Thoros their Baron; he gained possession of Vahka, and afterwards of many other places.
Let this be as it may, it was certainly ordained by God that this man, who was carried away as a prisoner, should become the chief of the country of his forefathers, that he should take the government out of the hands of the Greeks, and destroy their armies.In the same year /1151/ Leo's son, Thoros, took Mamistra and Tel Hamdoun from the Romans and seized Duke Thomas.
Duke Andronicus who was charged with protecting the land of the Cilicians by order of the Roman emperor, came to the city of Mamistra with 12,000 cavalry against Thoros.
Instead, placing his trust in God, he assembled his forces, breached Mamistra’s walls at night, and attacked /the Byzantine troops/ like a lion, putting them to the sword.
When he returned and saw what had unfolded everyone thanked God, for they had been defeated without the use of weapons and without a physical battle.Other view is that after the battle Raynald was forced to return home, covered with humiliation; and later on, Thoros voluntarily surrendered to the brethren the fortresses in question, and the Knights in turn took oath “to assist the Armenians on all occasions where they needed help.”[10]" The Armenians attacked the few remaining Byzantine fortresses in Cilicia.