Which 636 battle ended Byzantine control of Syria?

The Battle of Yarmouk in 636 ended effective Byzantine control of Syria.

Fought near the Yarmouk River, close to the modern borders of Syria and Jordan, the battle was a decisive victory for the Rashidun Caliphate over the Byzantine Empire. It formed part of the early Muslim conquest of the Levant, during which Arab armies captured or forced the abandonment of important Byzantine cities.

The fighting consisted of several engagements over roughly six days in August 636. Emperor Heraclius had assembled a large multinational force that included imperial troops, Armenians, and Christian Arab allies. The Muslim army, commanded by figures including Khalid ibn al-Walid and Abu Ubayda ibn al-Jarrah, concentrated its forces and defeated the Byzantine army in a strategically important position.

Yarmouk did not mean every Byzantine garrison disappeared immediately, and the wider conquest continued for several years. However, the defeat destroyed Byzantine hopes of recovering the region and made continued rule in Syria untenable. It is often remembered as one of the most consequential battles of the early medieval Middle East.