score:8
Because they had just lost the battle of Masts to Muawiya bin abu sufyan in the previous year (655). The emperor Constans II was almost killed.
And notice, when the pressure from the East was really weaker, in 668, he fought the Slavs to the North. And only in 659 "he campaigned far to the east, taking advantage of a rebellion against the Caliphate in Medina. The same year he concluded peace with the Arabs."
He had too little resources for too many problems. And simply couldn't recover Syria.