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Yangtze river campaign

With many Chinese ports now blockaded or under British occupation, Major General Gough sought to cripple the finances of the Qing Empire by striking up the Yangtze River. 25 warships and 10,000 men were assembled at Ningbo and Zhapu in May for a planned advance into the Chinese interior. The expedition's advance ships sailed up the Yangtze, and captured the emperor's tax barges, a devastating blow that slashed the revenue of the imperial court in Beijing to a fraction of what it had been.

On 14 June, the mouth of the Huangpu River was captured by the British fleet. On 16 June, the Battle of Woosung occurred, after which the British captured the towns of Wusong and Baoshan. The undefended outskirts of Shanghai were occupied by the British on 19 June. Following the battle, Shanghai was looted by retreating Qing bannermen, British soldiers, and local civilians. Qing admiral Chen Huacheng was killed while defending a fort in Woosong.

The fall of Shanghai left the vital city of Nanjing vulnerable. The Qing amassed an army of 56,000 Manchu bannermen and Han Green Standards to defend Liangjiang Province, and strengthened their river defences on the Yangtze. However, British naval activity in Northern China led to resources and manpower being withdrawn to defend against a feared attack on Beijing. The Qing commander in Liangjiang Province released 16 British prisoners with the hope that a ceasefire could be reached, but poor communications led both the Qing and the British to reject any overtures at peace. In secret, the Daoguang Emperor considered signing a peace treaty with the British, but only in regards to the Yangtze River and not the war as a whole. Had it been signed, the British forces would have been paid to not enter the Yangtze River.

On 14 July, the British fleet on the Yangtze began to sail up the river. Reconnaissance alerted Gough to the logistical importance of the city of Zhenjiang, and plans were made to capture it. Most of the city's guns had been relocated to Wusong and had been captured by the British when said city had been taken. The Qing commanders inside the city were disorganised, with Chinese sources stating that over 100 traitors were executed in Zhenjiang prior to the battle. The British fleet arrived off of the city on the morning of 21 July, and the Chinese forts defending the city were blasted apart. The Chinese defenders initially retreated into the surrounding hills, causing a premature British landing. Fighting erupted when thousands of Chinese soldiers emerged from the city, beginning the Battle of Chinkiang.

British engineers blew open the western gate and stormed into the city, where fierce street to street fighting ensued. Zhenjiang was devastated by the battle, with many Chinese soldiers and their families committing suicide rather than be taken prisoner. The British suffered their highest combat losses of the war (36 killed) taking the city.

After capturing Zhenjiang, the British fleet cut the vital Grand Canal, paralysing the Caoyun system and severely disrupting the Chinese ability to distribute grain throughout the Empire. The British departed Zhenjiang on 3 August, intending to sail to Nanking. They arrived outside the Jiangning District on 9 August, and were in position to assault the city by 11 August. Although explicit permission to negotiate had not yet been granted by the emperor, Qing officials inside the city agreed to a British request to negotiate.