The Siege of Damascus (634) lasts from 21 August to 19 September 634 before the city falls to the Rashidun Caliphate.

Damascus is the first major city of Constantinople’s empire to fall in the Muslim conquest of Syria.The last of Roman-Persian Wars had ended in 627, when Heraclius concluded a successful campaign against the Persians in Mesopotamia.

At the same time, Mohammad had united the Arabs under the banner of Islam.

After his death in 632, Abu Bakr had succeeded him as the first Rashidun Caliph.

Suppressing several internal revolts, Abu Bakr seeks to expand the empire beyond the confines of the Arabian Peninsula.

In April 634, Abu Bakr invades the Byzantine Empire in the Levant and decisively defeats a Byzantine army at the Battle of Ajnadayn.

The Muslim armies marches north and lays siege to Damascus.

The city is taken after a Monophysite bishop informs Khalid ibn al-Walid, the Muslim commander in chief, that it is possible to breach city walls by attacking a position only lightly defended at night.

While Khalid enters the city by assault from the Eastern gate, Thomas, commander of Byzantine garrison, negotiates a peaceful surrender at the Jabiyah gate with Abu Ubaidah, Khalid's second in command.

After the surrender of the city, the commanders dispute the terms of the peace agreement.

The commanders finally agree that the peace terms given by Abu Ubaidah will be met.

Although he acquiesces to the peace terms, three days after the surrender of the city Khalid chases after the Damascan refugees towards Antioch and defeats them in battle six days later, near present day Al Jayyad.