After an intermittent siege that lasted over ten years, Qing armies led by Jirgalang captured Songshan and Jinzhou in early 1642.

[citation needed] Seeing the progress of the rebels, on April 5, the Ming Chongzhen Emperor (Zhu Youjian) requested the urgent help of any military commandant in the empire.

[10] Eager to secure the loyalty of his military elite, on April 11 he granted the title of "earl" to four generals, including Wu Sangui and Tang Tong [zh] (唐通).

[12] On April 22, the Ming court learned that Tang Tong had surrendered to Li Zicheng the day before and that the rebels' army was now in Changping, 65 kilometers northwest of Beijing.

[citation needed] Soon after the Emperor called for help, powerful Ming general Wu Sangui left his stronghold of Ningyuan north of the Great Wall and started marching toward the capital.

On April 26, his armies had moved through the fortifications of Shanhai Pass (the eastern end of the Great Wall) and were marching toward Beijing when he heard that the city had fallen.

[18] Dorgon's Han Chinese advisors Hong Chengchou and Fan Wencheng (范文程) urged the Manchu prince to seize the opportunity of the fall of Beijing to claim the Mandate of Heaven for the Qing dynasty.

[21] Having instructed his brothers Ajige and Dodo to lead two wings of ten thousand men each to protect his flanks, Dorgon led his main force toward the Pass.

[21] At dawn on May 27, the main Qing army reached the gates of Shanhai Pass, where Dorgon received Wu Sangui's formal surrender.

[22] Historian Frederic Wakeman claims that by the late afternoon, Wu Sangui's army was on the verge of defeat when a "violent sandstorm" started blowing on the battlefield.

[22] Dorgon chose this moment to intervene: galloping around Wu's right flank, the Qing cavalry charged Li's left wing at Yipianshi ("Lone Rock", north of Shanhai Pass).

But Frederic Wakeman says such sources tend to inflate the number of Li Zicheng's troops because they wanted to emphasize the Qing's military prowess against the Shun.

[24] Mote, on the other hand, states that Wu had 80,000 men garrisoned in Ningyuan when he left that city for Shanghaiguan in April 1644, and that 20,000 to 30,000 militiamen also came to him unsolicited the day of the battle of Shanhai Pass.

[26] Angela Hsi, for her part, cites a contemporaneous source to argue that Wu led 40,000 troops ("one of the better military forces of the day") and that he was assisted by 70,000 residents of Liaodong (遼東), "who were reputed to be excellent fighters.

[30] On June 3, as a "final gesture of defiance" after his decisive defeat, Li officially declared himself Emperor of the Great Shun at the Wuying Palace (武英殿).

The elders and officials who went out of the city expecting to greet Wu Sangui and the Ming heir apparent were shocked when the leader of the victorious army turned out to be Prince Regent Dorgon of the Qing.

[40] After repressing revolts against Qing rule in Hebei and Shandong in the Summer and Fall of 1644, in October of that year Dorgon sent several armies to extirpate Li Zicheng from his Shaanxi stronghold.

Resistance to Qing rule was intensified by the "haircutting command" on July 21, 1645, which forced all Chinese men to adopt the clothing of the Manchus and shave their forehead, leaving their remaining hair tied into a queue.