Battle of Ajnadayn

The Battle of Ajnadayn (معركة أجنادين), fought on July 30, 634, in an unknown location close to Beit Guvrin in present day Israel; it was the first major pitched battle between the Byzantine (Roman) Empire and the army of the Arabic Rashidun Caliphate. The result of the battle was a decisive Muslim victory. The details of this battle are mostly known through Muslim sources, such as 9th century historian Al-Waqidi.

Background
According to David Nicolle, the Rashidun army left the capital Medina probably in the autumn of 633, but possibly at the beginning of 634. They first engaged and defeated the Byzantines at Dathin on February 4; after that Emperor Heraclius, then stationed in Emesa (now Homs, Syria), had reinforcements sent south to protect Caesarea Maritima. As a possible reaction commander Khalid ibn al-Walid was ordered to interrupt operations against the Sassanian Empire and reach Syria, which brought him to engage and defeat the Byzantine-allied Ghassanids by April 24, permitting him to enter almost unopposed in Bosra. At this point Khalid converged with several armies led by generals such as Abu_Ubaydah_ibn_al-Jarrah, Yazid ibn Abu Sufyan, Amr ibn al-A'as and Shurahbil Ibn Hasanah.

Khalid united with Amr's forces in a place known traditionally as Adjnadayn. No geographer has attested such a place, which probably originates from a conflation of the Arab plural adjinad (i.e. "armies"). All the same due to Arab sources the location of the battlefield has been found to have taken place in the wadi l'Samt at 9 km from modern Beit Guvrin, Israel.

The battle
Regarding the primary sources, first must be noticed the absence of any of Byzantine provenience; possibly, according to Walter Kaegi, because what Byzantine material we have may conflate the battle with other Byzantine defeats such as Dathin and Yarmouk. The earliest source appears to be an entry in the Frankish Chronicle of Fredegar compiled in 658-660, unless this is as possible an interpolation.

Regarding the strength of the confronting armies H. A. R. Gibb in the Encyclopaedia of Islam argues that at best both forces were made of 10,000 men and that Muslim sources are "highly exaggerated". Concerning the size of the Byzantine army, Nicolle also accepts this estimate as he puts it at 9,000-10,000 but instead considers the Rashidun forces to have been 15,000-18,000, a number placed at 20,000 by David Morray in the The Oxford Companion to Military History.