 The forces defending Kucha , consisting of 50 @,@ 000 soldiers , were lured and ambushed by Ashina . They chased after a group of 1 @,@ 000 horsemen employed by Ashina as a decoy , but encountered additional Tang forces that mounted a surprise attack . The Kuchean forces were defeated and retreated to Aksu , a nearby kingdom in the Tarim Basin . Ashina captured the king following a forty @-@ day siege , ending with the surrender of the Kucha forces on 19 January 649 . One of Ashina 's officers , acting as a diplomat , persuaded the chieftains of the region to surrender instead of fighting back . 
