In the waning years of the Umayyad dynasty, a caliphal army suffered a major defeat in an area that is now part of Afghanistan, to a Turkish people called the Turgesh. The defeat was serious enough to disrupt caliphal control of the region called Transoxiana (literally “across the Oxus River,” which is today known as the Amu Darya) and allowed the Turgesh to advance into the eastern Iranian region of Khurasan. The setback for the caliphate was temporary; the Arabs laid a whupping on the Turgesh later that year that led to their almost total disappearance as a threat. The setback for the Umayyad dynasty, however, was considerably more significant, because the loss of direct control over Khurasan helped set the conditions that allowed the Abbasid revolution to incubate there.
The Turgesh aren’t on the world stage very long, but we can’t very well talk about their victory without at least mentioning who they were. They’re a product of the Turkic Khanate, or Göktürk Khanate if you prefer, that controlled the Central Asian steppes from the mid-6th century through the mid-8th century after a lull in the middle of the 7th century. In the 580s a civil war split the khanate into eastern and western halves, and both then were toppled by the Tang, in 630 and 659, respectively, before the whole Turkic Khanate was revived in 682. The Turgesh are a product of the collapse of the western khanate in 659–they established their own khanate in 699 in a part of modern Kyrgyzstan and by the 710s they were strong enough that their khan, Suluk (d. 738), decided they were the ones who could drive these Umayyad invaders out of the parts of Transoxiana they’d only just conquered.
Beginning around 720 the Turgesh began to attack the Umayyads, and though the caliphate was obviously the larger empire and could in theory bring more forces to bear than the Turgesh, the caliphal armies were operating a long way from home in a place where they weren’t welcome. The local peoples of the region, primarily Sogdians, began revolting to coincide with stepped up Turgesh assaults; the largest of these, led by an Arab named al-Harith b. Surayj (d. 746), also tapped into simmering resentments about the treatment of non-Arabs living in the empire. Things got bad enough that in the mid-730s, the caliph, Hisham b. Abd al-Malik (d. 743) sent a former governor of Khurasan, the experienced Asad b. Abdullah al-Qasri (d. 738) back east to put a lid on it. Asad quickly was able to tamp down Harith’s revolt, then turned his attention to the Turgesh.Asad targeted Khuttal, a local Iranian statelet in the vicinity of modern Tajikistan that had supported Harith and the Turgesh, but Suluk responded to the threat to his ally. Asad sent his baggage train, loaded with goodies looted from Khuttal, back toward the Oxus, which made sense, but then when Suluk’s army showed up it appears that Asad’s forces pretty much turned and ran. Suluk’s army defeated the Arab rearguard and then pursued the main body of the army across the river. But after failing to take the Arab encampment, he turned his attention to the nearby baggage train (hence the name), and his forces were able to take it after slaughtering most of the defenders. Now that I think about it, this “Battle of the Baggage” isn’t really much of a battle, but what can you do? We’re here for the aftermath, not the battle itself.
Suluk’s victory seems to have made him a little cocky, and he wound up paying for it pretty quickly. Asad, having survived the battle, ensconced himself in his Khurasanian capital, Balkh (which is a small town in northern Afghanistan today but used to be one of the largest cities in the world before successive Mongolian sackings in the 13th-14th centuries left it mostly in ruins) and planned to ride out the winter, as was typical Arab practice. But Suluk, along with Harith, decided to invade Khurasan, and Asad promptly defeated them at the Battle of Kharistan in December. Suluk was then assassinated by his men and the Turgesh khanate was plunged into civil war. Harith dropped off the map for a couple of years but resurfaced in the 740s first as a supporter of the then-governor of Khurasan, Nasr b. Sayyar (d. 748), and then at the head of another rebellion–this time, he was defeated and killed.
Though Asad was ultimately successful in defeating the Turgesh and Harith at Kharistan, and Umayyad control over Khurasan was never really threatened (they did lose control over part of Transoxiana, but only temporarily), the losses he suffered to his mostly-Syrian army and allied Iranian tribes crippled the Umayyads’ ability to directly rule over Khurasan. Grievances–between Arabs and non-Arabs, between Arabs of different tribes, between Syrians and everybody else–that were already obviously high continued to build up in the province, and without a large enough army to maintain control by force, it was inevitable that another revolt would break out. In fact, several revolts wound up breaking out, but they eventually coalesced, or were made to coalesce, around the rebellion that ultimately overthrew the Umayyads and brought the Abbasids to power.