Constantine IV was a Byzantine Emperor who ruled from 668 to 685 AD. He was the son of Emperor Constans II and is best known for his military campaigns against the Arabs, particularly during the Second Arab Siege of Constantinople in 674-678. His leadership helped to secure the city and maintain the Byzantine Empire's power. During his reign, Constantine IV also convened the Third Council of Constantinople in 680-681, which addressed the Monothelite controversy, a theological dispute regarding the nature of Christ. His efforts in both military and religious matters contributed to the stability of the empire during a challenging period.