The siege of Kucha, lasting forty days, culminated in the surrender of the city's defenders to the forces led by Tang dynasty general Ashina She'er. The backdrop to this military endeavor was rooted in the Tang dynasty's aspirations to project power and establish dominance over the Northern Tarim Basin in Xinjiang, an area critical for the trade routes connecting China to Central and Western Asia. Kucha, as a prominent oasis city along the Silk Road, was strategically important not only for its economic significance but also for its cultural and political connections to surrounding regions.

The siege began as Tang forces, mobilizing under She'er’s command, implemented a strategy of encirclement and blockading to cut off supplies and reinforcements to Kucha. The prolonged pressure forced the local rulers to reconsider their position against the dominant Tang empire. Through a series of military actions and psychological tactics, the Tang general aimed to demoralize the opposition while showcasing the might of the Tang military machine. Defenders resisted valiantly; however, the sustained onslaught led to dwindling resources and eventual capitulation.

The fall of Kucha was pivotal for the Tang dynasty as it opened up greater opportunities for expansion into Central Asia and laid the groundwork for a more interconnected economic and cultural landscape. Following the siege, the Tang's ability to control the Silk Road improved significantly, allowing for increased trade and cultural exchanges between the East and the West, which would have lasting effects on the region’s history.