Ansi City

The city was founded in early 4th century after Goguryeo conquered the area, and received its name from a Han dynasty prefecture of the same name.

After the battle of Mount Zhubi, the Goguryeo fell back on their city of Ansi and the Tang army pursued.

Emperor Taizong was insulted, and Li Shiji received permission to slaughter the city's male inhabitants when it fell—which led to the Ansi defenders fighting even harder.

Go Yeonsu and Go Hyezin, who had by now accepted Tang titles, suggested:[citation needed] Since we, your slaves, have now submitted to the empire, we have to give you all we have.

Once you collect the supplies in these cities, march forward, and Pyongyang will not be able to stand.Some other officials also suggested:[citation needed] Zhang Liang is at Beisha.

If you order him to rendezvous with us, he will arrive in two days, and with the entire Goguryeo state in fear, we can then capture Ogol, cross the Yalu River, and attack Pyongyang, and we will be easily successful.Emperor Taizong was inclined to accept these proposals, but Zhangsun opposed, stating:[citation needed] The nature of a campaign commanded by a Son of Heaven is different from the nature of a campaign commanded by a mere general.

It will be more secure to first capture Ansi and Geonan, and then march deep into Goguryeo territory.Emperor Taizong agreed with Zhangsun and did not head toward Ogol.

[citation needed] As the siege continued, on an occasion, when Emperor Taizong heard the sounds of chickens and pigs coming out of the city, he opined to Li Shiji that it must be that the Goguryeo defenders were preparing an assault and were slaughtering animals beforehand to feast on them.

At this moment, Fu, for reasons unexplained in history, left his position, and the Goguryeo forces took the opportunity to attack and capture the dirt mound, and instead used it as part of the defensive bulwarks.

Emperor Taizong, in anger, executed Fu in public and ordered a heavy assault on the dirt mound, but could not capture it within three days.