Nestorian missionaries are the alleged builders of the Daqin Pagoda in Chang'an (Shaanxi).

Daqin is the name for the Roman Empire in the early Chinese language documents of the first and second centuries.

First attested in 1064, when the Chinese poet Su Shi visited it and wrote a well-known poem about it, "Daqin Temple".

details that suggest that the monastery was earlier a Christian church include a supposed depiction of Jonah at the walls of Nineveh, a nativity scene (depiction of the birth of Jesus) and Syriac graffiti.

The east-facing orientation of the complex is also advanced as evidence of its Christian origin, since Chinese Taoist and Buddhist temple complexes face north or south.

The claims are controversial.

Emperor Taizong of the Tang Dynasty begins a campaign against the Xiyu states in the Tarim Basin.

Qu Wentai, the king of Gaochang, a Xiyu state n the Tarim Basin, around the new year of 640 forms an alliance with Western Tujues who are hostile to Tang.

Emperor Taizong sends Hou Junji, assisted by Xue Wanjun, to attack Gaochang.

Qu Wentai, when Hou arrives at Gaochang, dies and is succeeded by his son Qu Zhisheng.

Rejecting a proposal by some of his generals to ambush the Gaochang nobles when they are burying Qu Wentai (finding that doing so would be immoral), he puts Gaochang's capital under siege, forcing Qu Zhisheng to surrender.

Emperor Taizong annexes Gaochang territory except for three cities, which Gaochang had seized from Yanqi, and which are therefore returned to Yanqi after the king of Yanqi meets with Hou to congratulate him.

Hou returns to the Tang capital Chang'an with Qu Zhisheng and his subordinates as captives.