[1] Despite being a childhood friend of Wu's founding emperor, Sun Quan, he was never given an important position or assignment before Lü Meng's invasion of southern Jing Province in 219, wherein he assisted in capturing the enemy commander, Guan Yu.

Zhu Ran was sent to the northwestern border, where he defended the city of Jiangling with only 5,000 troops against an enemy force about ten times greater.

[3] During his tenure as an commandery administrator, Zhu Ran had the merit of subjugating the Shanyue ethnic group within his jurisdiction, and was able to do so in less than a month.

Heeding Lü Meng's dying words, Sun Quan gave the staff of authority to Zhu Ran, and tasked him with the defence of Jiangling County, the capital of Nan Commandery and a vital strategic stronghold on the frontline.

After breaking Liu Bei's vanguard, Zhu Ran's forces took up a position at the rear of the Shu army, blocking their escape as they attempted to flee from a fire attack executed by Lu Xun.

Together, Lu Xun and Zhu Ran pursued Liu Bei into the deep hills, pushing him back to Baidicheng, where he would admit defeat and die shortly afterwards.

Even though Cao Pi's plan was detected by Lu Xun, who ordered Xu Sheng to perform a double-back to return to Wuchang (present-day Ezhou, Hubei) and informed Sun Quan to prepare for war, the Wu forces still faced a dire situation.

Their troops were stretched thinly across at least four fronts; on the western front facing Baidicheng, where Liu Bei's declaration of war was still in effect; Nan Commandery (around present-day Jingzhou, Hubei), which was pressed by the Wei generals Zhang He, Xu Huang, Cao Zhen, and Xiahou Shang; at Ruxu (on the eastern side of Lake Chaohu in present-day Anhui), where the Wei general Cao Ren was leading his team to land on Zhongzhou; and at the eastern battlefield on the Yangtze, Dongkou (along the Yangtze near present-day Liyang, Jiangsu), where Zhang Liao and Zang Ba under the command of Cao Xiu defeated Lü Fan's navy.

Furthermore, an outbreak of disease greatly reduced the morale and number of soldiers in Zhu Ran's army, leaving him with only 5,000 men capable to do battles, who were intimidated by the news that the Wu reinforcements led by Sun Sheng (孫盛) were eliminated by Zhang He.

At Jiangling County, Xiahou Shang had also built numerous pontoon bridges for his soldiers to cross the shallow waters and attack the castle.

Not knowing how and where the Wei forces were crossing the shallows of the river, the Wu reinforcements under Pan Zhang and Zhuge Jin had no effective way to lift the siege.

Surrounded in his castle, Zhu Ran was heavily outnumbered by Cao Zhen, who encircled the fortress with several layers and deployed a variety of siege weapons.

Six months had passed; however, the Wei army still continued the siege, and Cao Pi had arrived at Wan city to bolster their morale.