Victory belonged to the Byzantines, and now, the honours of the war were even.
However, the Persian threat was not yet diminished.
The long-awaited assault on Constantinople was finally beginning to materialize — the Avars began moving siege equipment towards the Capital (the siege began on June 29, 626) whilst Shahrbaraz was ordered by King Khosrau II to send his army to Chalcedon and link up with the Avars.
Khosrau began conscripting able-bodied men into a new army, raising a crack force of approximately 50,000 men.
Heraclius, it seems, was not only being outmaneuvered, but being outmaneuvered by several larger armies.
However, Heraclius attempted to match the Persians by duplicating their strategy and dividing his forces into three separate contingents.
One army would defend the capital, whilst another, under the command of the Emperor's brother Theodore, would face the 50,000 conscripts in Mesopotamia who were commanded by the Persian General Shahin.
Meanwhile, the third, which would be personally commanded by the Emperor, would march through Armenia and the Caucasus and into Persia, which he believed would have been stripped of most of the able-bodied men due to Khosrau's conscription.
This would allow his forces to easily advance into the heartland of Persia.

Theodore's contingent fared well against Shahin in Mesopotamia, inflicting a crushing defeat on the Persians.
During this battle, at Constantinople, the city was well defended with a force of some 12,000 cavalry (presumably dismounted), supported by the entire city's population.
Indeed, the efforts of the Patriarch Sergius in whipping up the population into a religious and patriotic frenzy cannot be overlooked.
When the Byzantine fleet annihilated a Persian and an Avar fleet in two separate ambushes, the besiegers appeared to have withdrawn in panic.
And when word of Theodore's victory in Mesopotamia came, it was concluded by the besiegers that Byzantium was now under the protection of the Romans' Christian God.
Victory belonged to the Byzantines, and now, the honours of the war were even. However, the Persian threat was not yet diminished. The long-awaited assault on Constantinople was finally beginning to materialize — the Avars began moving siege equipment towards the Capital (the siege began on June 29, 626) whilst Shahrbaraz was ordered by King Khosrau II to send his army to Chalcedon and link up with the Avars. Khosrau began conscripting able-bodied men into a new army, raising a crack force of approximately 50,000 men. Heraclius, it seems, was not only being outmaneuvered, but being outmaneuvered by several larger armies. However, Heraclius attempted to match the Persians by duplicating their strategy and dividing his forces into three separate contingents. One army would defend the capital, whilst another, under the command of the Emperor's brother Theodore, would face the 50,000 conscripts in Mesopotamia who were commanded by the Persian General Shahin. Meanwhile, the third, which would be personally commanded by the Emperor, would march through Armenia and the Caucasus and into Persia, which he believed would have been stripped of most of the able-bodied men due to Khosrau's conscription. This would allow his forces to easily advance into the heartland of Persia.
Theodore's contingent fared well against Shahin in Mesopotamia, inflicting a crushing defeat on the Persians. During this battle, at Constantinople, the city was well defended with a force of some 12,000 cavalry (presumably dismounted), supported by the entire city's population. Indeed, the efforts of the Patriarch Sergius in whipping up the population into a religious and patriotic frenzy cannot be overlooked. When the Byzantine fleet annihilated a Persian and an Avar fleet in two separate ambushes, the besiegers appeared to have withdrawn in panic. And when word of Theodore's victory in Mesopotamia came, it was concluded by the besiegers that Byzantium was now under the protection of the Romans' Christian God.
Byzantine Empire under the Heraclian dynasty