Since the beginning of the
Muslim conquests, the
Byzantine Empire, as the largest, richest, and militarily strongest state bordering the expanding
Caliphate, had been the Muslims' primary enemy. Following the disastrous
Battle of Sebastopolis, the Byzantines had largely confined themselves to a strategy of passive defence, while the Muslim armies regularly launched raids into Byzantine-held
Anatolia. Following their
failure to capture the Byzantine capital,
Constantinople, in 717–718, the
Umayyads for a time diverted their attention elsewhere. From 720/721, however, they resumed their expeditions against Byzantium in a regular pattern: each summer one or two campaigns (pl. ''ṣawā'if
, sing. ṣā'ifa
) would be launched, sometimes accompanied by a naval attack and sometimes followed by winter expeditions (shawātī''). These were no longer aimed at permanent conquest but were rather large-scale raids, plundering and devastating the countryside, and only occasionally attacking forts or major settlements. The raids of this period were also largely confined to the
central Anatolian plateau (chiefly its eastern half,
Cappadocia), and only rarely reached the peripheral coastlands. Under the more aggressive Caliph
Hisham ibn Abd al-Malik (), the Arab raids became more substantial affairs and were led by some of the Caliphate's most capable generals, including princes of the Umayyad dynasty, such as
Maslama ibn Abd al-Malik or Hisham's own sons
Mu'awiyah,
Maslama, and
Sulayman. Gradually, however, the Muslim successes became fewer, especially as their resources were drawn into the
mounting conflict with the
Khazars in the
Caucasus. The raids continued, but the Arab and Byzantine chroniclers mention fewer successful captures of forts or towns. Nevertheless, in 737 a major victory over the Khazars allowed the Arabs to shift their focus and intensify their campaigns against Byzantium. Thus in 738 and 739 Maslamah ibn Hisham led successful raids, including the capture of the town of
Ancyra. For the year 740, Hisham assembled the largest expedition of his reign, appointing his son Sulayman to lead it. ==Battle==