Zhang Xianzhong
In the early 17th century, persistent drought and famine driven by the Little Ice Age accelerated the collapse of the Ming dynasty. Two major popular uprisings swelled up, led by Zhang Xianzhong and Li Zicheng, both poor men from famine-hit Shaanxi who took up arms in the 1620s. At the same time, Ming armies were occupied in the defence of the northern border against the Manchu ruler Hong Taiji, whose father, Nurhaci, had united the Manchu tribes into a cohesive force. In 1636, after years of campaigns against Ming fortifications north of the Great Wall, Huangtaiji declared himself emperor of the Qing dynasty.