Constans was the last attested emperor to serve as consul, in 642,[9][10][d] although the office continued to exist until the reign of Leo VI the Wise (r.

[13] His religious policy saw him steering a middle line in disputes between the Orthodox and Monothelites by refusing to persecute either and prohibited discussion of the natures of Jesus Christ under the Type of Constans in 648.

In September 641, the 10-year old Constans II was crowned co-emperor due to rumors that Heraclonas and Martina poisoned Constantine III.

Later that same year, on or around 5 November, Heraclonas was deposed by Valentinus, one of Heraclius’ most trusted generals, and Constans II was left as sole emperor.

Under Constans, the Byzantines completely withdrew from Egypt in 642, and the third Rashidun caliph Uthman (r. 644–656) launched numerous attacks on the islands of the Mediterranean and Aegean Seas.

A Byzantine fleet under the admiral Manuel occupied Alexandria again in 645, and the Alexandrians hailed him as a liberator, since the caliphate levied heavier taxes and showed less respect for their religion.

However, Manuel squandered his time and popularity in plundering the countryside, and eventually the Arab army managed to force him to embark for home.

[19] The situation was complicated by the violent opposition to Monothelitism by the clergy in the west and the related rebellion of the Exarch of Carthage, Gregory the Patrician.

In 658, with the eastern frontier under less pressure, Constans defeated the Slavs in the Balkans, temporarily reasserting some notion of Byzantine rule over them and resettled some of them in Anatolia (c. 649 or 667).

Although on friendly terms with Vitalian, he stripped buildings (including the Pantheon) of their ornaments and bronze to be carried back to Constantinople, and in 666 declared the Pope to have no jurisdiction over the Archbishop of Ravenna, since that city was the seat of the Exarch, his immediate representative.

[25] However, John Haldon states that this idea is not supported by a "a shred of evidence", although redistribution of the armies across the Anatolian provinces did take place, and likely resulted in administrative changes.

[32] These are recorded as having begun in the year 643 with an embassy sent by the king Boduoli (波多力, Constans II Pogonatos) to Emperor Taizong of Tang, bearing gifts such as red glass and green gemstones.

[32] The Byzantine historian Theophylact Simocatta, writing during the reign of Heraclius (r. 610–641), relayed information about China's geography, its capital city Khubdan (Old Turkic: Khumdan, i.e. Chang'an), its current ruler Taisson whose name meant "Son of God" (Chinese: Tianzi), and correctly pointed to its reunification by the Sui dynasty (581–618) as occurring during the reign of Maurice, noting that China had previously been divided politically along the Yangzi River by two warring nations.