[3] However, he was severely criticized by some contemporaries and some later historians as lacking humanity due to his encouragement of cannibalism during the Battle of Suiyang.

It was said that at that time, the large clans of the county were both powerful and treacherous, and one of the local officials from one of those clans, Hua Nanjin (華南金), was so dominant at the county government that the people often said, "What comes from Hua Nanjin's mouth is as good as what comes from the hand of the government."

[7] Late in 755, while Zhang Xun was still serving at Zhenyuan County, the general An Lushan rebelled at Fanyang Circuit (范陽, headquartered in modern Beijing) and quickly advanced south to capture the Tang eastern capital Luoyang, where he declared himself the emperor of a new state of Yan.

One of his generals, Zhang Tongwu (張通晤), advanced east from Luoyang and led to the submission of a number of Tang officials, including Zhang Xun's superior Yang Wanshi (楊萬石), the governor of Qiao Commandery (譙郡, roughly modern Zhoukou).

He selected 1,000 men and took them to Yongqiu, where fellow Yan-resistor Jia Bi (賈賁) had taken up position to defend against the Tang-official-turned-Yan-general Linghu Chao (令狐潮).

When Linghu counterattacked, Jia died in battle, and Zhang became solely in command of Tang forces in defense of Yongqiu.

He sent a letter submitting to the general in command of the Tang troops in the region, Li Zhi (李祇) the Prince of Wu, and Li Zhi bestowed him the title of imperial censor to give him official command of the forces at Yongqiu.

Zhang feigned agreement, and the next morning, he displayed a portrait of Emperor Xuanzong and led the soldiers in bowing to it, and then summoned the six officers and executed them.

With Yongqiu not falling to him, Linghu was again forced to lift the siege and withdraw to Chenliu (陳留, in modern Kaifeng, Henan).

[10] Yin Ziqi launched repeated attacks on Suiyang, each time repelled by Zhang Xun.

Meanwhile, though, the food supplies—which Xu Yuan had initially gathered plenty of in anticipation of a siege but which Li Ju had forced Xu to partially give to two other commanderies, Puyang (濮陽, roughly modern Puyang, Henan) and Jiyin (濟陰, roughly modern Heze, Shandong)—began to run out.

By summer 757, Suiyang was in desperate straits, with the soldiers forced to eat a mixture of rice, tea leaves, paper, and bark.

He gave his officer Nan Jiyun (南霽雲) 30 cavalry soldiers and had Nan fight his way out of the siege, to head to Linhuai (臨淮, in modern Huai'an, Jiangsu) to seek aid from the Tang general Helan Jinming (賀蘭進明), who had the strongest Tang force in the area.

Zhang and Xu discussed the proposal, but eventually decided to keep defending the city, believing that abandoning Suiyang would allow Yan forces to attack and capture the region between the Huai River and the Yangtze River, and that given how weak their troops were, they could not escape disaster even if they abandoned Suiyang.

Yin therefore executed Zhang and 36 key officers under him, including Nan Jiyun and Lei Wanchun (雷萬春).

[11] After Emperor Suzong returned to Chang'an, he posthumously honored a large number of officials who stayed faithful to Tang and died fighting the Yan forces.

Zhang Xun and his deeds were highly praised by many later scholars, government officials, and writers.