Excerpts from Books and Wikipedia
"Constans, fourteen when he came to the throne, had watched Egypt and North Africa fall to the Arabs at the same time that Italy was breaking away. Now, in 661, he was thirty years old, father of three sons . . . He had assumed control of the empire, and the civil war in Lombardy gave him a plan. The Arab assault may have seemed unstoppable, but Italy was vulnerable; Constans II decided to leave Constantinople, set up his campaign headquarters in Tarentum, on the instep of the Italian boot, and reconquer the peninsula. . . . By 663, Constans II was established in Tarentum and carrying on a reasonably successful war against the Lombard holdings in the south. . . . He landed on the island, went to Syracuse, and declared it to be his new capital. His intention to reclaim Rome hadn’t survived his first sight of the city. He had been imagining glories, but the real city—shabby, depopulated, demoralized—seemed beyond repair. From Syracuse, he again began to launch attacks on the south of Italy. He ruled the island like an emperor of old: despotic, demanding, and imperious. . . . his tyrannical behavior made him unpopular;" He was killed by one of his servants. [Bauer: Medieval World, p. 320-1]