《新唐书·列传·卷七十八》
仙芝征伐大食，围困了怛逻斯城，碰到敌人救兵来了，仙芝的军队撤退，部下都失散了。
仙芝讨大食，围怛逻斯城。会虏救至，仙芝兵却，士相失。
Xianzhi attacked the Umayyad Caliphate and besieged the city of Talas. When reinforcements from the enemy arrived, Xianzhi's army retreated, and his subordinates were scattered.
<s>[INST] Identify the key themes in this Classical Chinese text and explain them in English: 仙芝讨大食，围怛逻斯城。会虏救至，仙芝兵却，士相失。 [/INST] Xianzhi attacked the Umayyad Caliphate and besieged the city of Talas. When reinforcements from the enemy arrived, Xianzhi's army retreated, and his subordinates were scattered.</s>
Identify the key themes in this Classical Chinese text and explain them in English: 仙芝讨大食，围怛逻斯城。会虏救至，仙芝兵却，士相失。
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Xianzhi attacked the Umayyad Caliphate and besieged the city of Talas. When reinforcements from the enemy arrived, Xianzhi's army retreated, and his subordinates were scattered.
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