Ḥaydar ibn Kāwūs (Arabic: حيدر بن كاوس, Persian: خِیذَر اِبنِ کاووس, romanized: Kheyzar ebn-e Kāvus), better known by his hereditary title of al-Afshīn (Arabic: الأفشين, Persian: اَفشین, romanized: Afshin), was a senior general of Sogdian Iranian descent at the court of the Abbasid caliphs and a vassal prince of Oshrusana.

[4] At the time of the first Arab invasion of Transoxiana (including Oshrusana) under Qutayba ibn Muslim (94-5 AH/712-14 CE), Ushrusana was inhabited by Iranians,[1] who were ruled by their own princes who bore the traditional title of Afshin.

[10] The confusion comes from the fact that the term “Turk” was used loosely by Arab writers of the time to denote the new troops of the caliph despite the inclusion among them of some elements of Iranian origin, including Ferghana and Oshrusana.

[14] According to Yaqubi, during the reign of the third Abbasid caliph Al-Mahdi (775-85), Afshin of Oshrusana was mentioned among several Iranian and Turkish rulers of Transoxania and the Central Asian steppes who submitted nominally to him.

[2] But it was not until Harun al-Rashid's reign in 794-95 that al-Fadl ibn Yahya al-Barmaki led an expedition into Transoxania and received the submission of Afshin Kharākana, the ruling Akin.

However, shortly after Ma'mun arrived in Baghdad from the east (817-18 or 819-20), a power struggle and dissension broke out among the reigning family of Oshrusana.

According to most of the sources, al-Ma'mun's heir, Al-Mu'tasim seconded high-ranking officers to serve under him and ordered exceptionally large salaries, expense allowances, and rations for him.

In 835, Caliph al-Mu'tasim appointed Afshin as governor of Adharbayjan[17] to fight against Babak Khorramdin, leader of neo-Mazdakite Persian movement of the Khurramites.

The latter was probably the largest city in Asia Minor at the time, as well as the birthplace of the reigning Amorian dynasty and consequently of particular symbolic importance; according to the chronicles, al-Mu'tasim's soldiers painted the word "Amorium" on their shields and banners.

[21][22] Afshin's force included, according to Skylitzes, the entire Arab army of Armenia, and numbered 20,000 (Haldon) to 30,000 men (Treadgold), among whom were some 10,000 Turkish horse-archers.

[21][23] In mid-June 838, Afshin crossed the Anti-Taurus Mountains and encamped at the fort of Dazimon, between Amaseia and Tokate, a strategically important location which the Byzantines also used as a forward staging area.

Looting the countryside as they advanced, they arrived before Amorium seven days after their departure from Ancyra, and began their siege of the city on 1 August.

The defenders tried to protect the wall by hanging wooden beams to absorb the shock, but they splintered, and after two days a breach was made.

[27][28][29] In the event, the city fell by treachery in mid-August, when the Byzantine officer commanding the breach tried to open up separate negotiations with al-Mu'tasim, and the Abbasids used the lull in order to launch a surprise attack.

He explained that when he punished a pair of Muslim fanatics destroying idols in Ushrusanah he was exercising reasonable leadership aimed at maintaining the harmony of his religiously diverse territory.