A General - Yuan Chonghuan

Yuan Chonghuan (袁崇煥) was a military general during the late-Ming Dynasty. He is best known for defending the Ming borders against Jurchen invasion.

As a young man, Yuan had a strong interest in military affairs. He travelled the country and frequently chatted with retired soldiers. Yuan started his career as a magistrate, but soon moved to the Ministry of War. At that time, the Ming borders were constantly being threatened by the Jurchens. On one occasion, Yuan travelled alone to the front lines to survey the situation. When he returned to the capital, he asserted that he could defend the borders if he was given the necessary resources. He was assigned to the frontier and given funds to recruit troops.

At the frontier, Yuan gained the trust of his superior and persuaded him to build a defensive line consisting of posts beyond the Great Wall. Yuan was tasked with fortifying the city of Ningyuan (寧遠). However, when a new commander took over, he changed strategies and ordered all troops to retreat to the Great Wall. Yuan refused the order and was left to defend Ningyuan with only 10,000 men. Jurchen chief Nurhaci (努爾哈赤) got news of the retreat and led an army of 130,000 soldiers to attack Ningyuan. The Jurchens laid siege on the city, but the Ming defenders fended them off with cannon fire. Yuan had reportedly spent much time studying the cannons to ensure it would fire accurately. Nurhaci suffered injuries from a cannon shot and would later die of his wounds. The Battle of Ningyuan was Nurhaci’s first and only major military loss to the Ming.

Following Yuan’s victory, he was put in charge of the forces at the frontier. As the Jurchens shifted their focus on attacking Korea, Yuan took the opportunity to rebuild the defensive line that he had envisioned. The defensive line stretched approximately 200 km, starting with the Shanhai Pass (山海關) at the Great Wall, extending to Ningyuan, and ending at Jinzhou (錦州). When Nurhaci’s successor, Hong Taiji (皇太極), led an army to invade the Ming border, he was repealed by the defense forces in Jinzhou and Ningyuan, proving the effectiveness of Yuan’s strategy.

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Despite scoring a second major victory against the Jurchens, Yuan was forced into retirement by the eunuch faction, who sent criticisms of Yuan to the emperor. However, Yuan was recalled the next year by the newly-enthroned Chongzhen Emperor (崇禎帝). He was given full authority for military affairs on the frontier. Using this authority, he executed a Ming general named Mao Wenlong (毛文龍) on charges of corruption. Mao was a general that was stationed in the Korean Peninsula. His position kept the Jurchens in check because if they attempted a massive invasion of the China proper, they risked an attack by Mao on the eastern front. But Yuan likely despised Mao’s arrogant behaviour and spending, or perhaps felt threatened by him. Mao’s execution caused the Chongzhen Emperor to be dissatisfied with Yuan.

The elimination of Mao provided the Jurchens with a prime opportunity to attack. This time, instead of attacking in the northeast region where Yuan was stationed, Hong Taiji travelled through Mongolia and attacked in the west. It marked the first time the Jurchens were able to breach the Great Wall. They reached the walls of Beijing before Yuan arrived with reinforcements to drive them away. Subsequently, Hong Taiji spread rumours that he had colluded with Yuan. Already unhappy with Yuan over the execution of Mao, the Chongzhen Emperor ordered for his arrest and sentenced him to death by slow slicing.

After the death of Yuan, the Ming army was no longer able to contain the Jurchens. The Jurchens breached the Great Wall several more times, causing countless deaths and plundering the region. The Ming Dynasty was thrown into disarray and would soon fall at the hands of rebels.

Yuan was posthumously cleared of treason during the Qing Dynasty.

Credits to Wikipedia user Evawen (English labels added)

Related:
A Scholar - Zuo Guangdou
A Eunuch - Wei Zhongxian