Arab–Byzantine prisoner exchanges

During the course of the Arab–Byzantine wars, exchanges of prisoners of war became a regular feature of the relations between the two powers, beginning in the late 8th century and continuing until the mid-10th century.

Background
Centuries of war between the Byzantine Empire and the Arab Caliphate had led to degree of a mutual understanding, respect, and a regular pattern of diplomatic and cultural exchanges between the two powers. This is evidenced for instance in the protocols for the imperial receptions at the Byzantine court, where the "Eastern Muslims" are accorded the first place immediately after any ecclesiastical officials, enjoying precedence over the Bulgarians or the Franks, but also by the humane treatment of prisoners of war by both sides. On the Byzantine side, Arab prisoners were usually paraded in triumphal processions but otherwise generally well treated. Senior figures were state prisoners and honoured guests for the duration of their captivity, being regularly invited to attend races at the Hippodrome or imperial banquets at the Great Palace and given gifts as part of imperial ceremonies. The rank and file were usually sold off as slaves or kept in prison until they were ransomed or exchanged. Most were employed as labour force, and although aome might be induced to convert to Christianity, in which case they were given lands to settle, otherwise they enjoyed the freedom to worship at mosques of their own. Muqaddasi notes that although the Arab captives were made to work as slaves, they could earn money, and that the Byzantines "do not force any of them to eat pork, and they do not slit their noses or their tongues".

Both sides also engaged in regular exchanges of prisoners (ἀλλάγια, allagia, in Greek), which took place on the river Lamos (mod. Limonlu Çayı) in Cilicia, on the border between Byzantium and the Caliphate. A truce was arranged beforehand, and both sides met on the river. The exchange was made man for man, as illustrated by al-Tabari in his report of the 845 exchange: Two bridges were built over the river, one for the prisoners of each side. Each side released one prisoner, who walked across the bridge towards his co-religionists, simultaneously with his counterpart. After the exchange was complete, the surplus prisoners were either ransomed for money or exchanged for slaves.

Prisoner exchanges
What is notable in the numbers reported for the exchanges, according to Arnold Toynbee, is that even in 845, before the Byzantines gained the upper hand in the Battle of Lalakaon (863), they held more prisoners than the Arabs, despite the wholesale capture and deportation of Byzantine subjects in events like the Sack of Amorion in 838. According to Toynbee, this attests to the efficiency of the Byzantine military's strategy of "dogging and pouncing" the Muslim armies that raided Asia Minor.