It began when the Rashidun army, under the command of Abu Ubayda, besieged Jerusalem beginning in November 636. After six months, the Patriarch Sophronius agreed to surrender, on condition that he submit only to the Caliph. According to Islamic tradition, in 637 or 638, Caliph Umar (r. 634–644) traveled to Jerusalem in person to receive the submission of the city. The Patriarch thus surrendered to him.

The Muslim conquest of the city solidified Arab control over Palestine, which would not again be threatened until the First Crusade in 1099. Jerusalem was an important city of the Byzantine province of Palaestina Prima. Just 23 years prior to the Muslim conquest, in 614, it fell to an invading Sassanid army under Shahrbaraz during the last of the Byzantine–Sasanian Wars. The Persians looted the city, and are said to have massacred its 90,000 Christian inhabitants.^[2] As part of the looting, the Church of the Holy Sepulchre was destroyed and the True Cross captured and taken to Ctesiphon as a battle-captured holy relic. The Cross was later returned to Jerusalem by Emperor Heraclius after his final victory against the Persians in 628. The Jews, who were persecuted in their Christian-controlled homeland, initially aided the Persian conquerors.^[3]   

After the death of the Islamic prophet Muhammad in 632, Muslim leadership passed to Caliph Abu Bakr (r. 632–634) following a series of campaigns known as the Ridda Wars. Once Abu Bakr's sovereignty over Arabia had been secured, he initiated a war of conquest in the east by invading Iraq, then a province of the Sassanid Persian Empire; while on the western front, his armies invaded the Christian Byzantine Empire.^[4]

In 634, Abu Bakr died and was succeeded by Umar (r. 634–644), who continued his own war of conquest.^[5] In May 636, Emperor Heraclius (r. 610–641) launched a major expedition to regain the lost territory, but his army was defeated decisively at the Battle of Yarmouk in August 636. Thereafter, Abu Ubayda, the Rashidun commander-in-chief of the Rashidun army in Syria, held a council of war in early October 636 to discuss future plans. Opinions of objectives varied between the coastal city of Caesarea and Jerusalem.

Abu Ubayda could see the importance of both these cities, which had resisted all Muslim attempts at capture. Unable to decide on the matter, he wrote to Caliph Umar for instructions. In his reply, the caliph ordered them to capture the latter. Accordingly, Abu Ubayda marched towards Jerusalem from Jabiyah, with Khalid ibn al-Walid and his mobile guard leading the advance. The Muslims arrived at Jerusalem around early November, and the Byzantine garrison withdrew into the fortified city.^[1]