Zizhi Tongjian, often shortened to Tongjian, is a multivolume chronicle compiled by the Northern Song historian Sima Guang. It consists of 294 volumes and took nineteen years to complete. Organized primarily by time, with events as its entries, it begins in 403 BCE, the twenty-third year of King Weilie of Zhou, and ends in 959 CE, the sixth year of the Xiande era under Emperor Shizong of Later Zhou, when the campaign in Huainan was halted. It covers 1,362 years of history across sixteen dynasties. In the book, the compilers distilled many lessons from the past for rulers to learn from. Emperor Shenzong of Song believed that "the past serves as a mirror, offering guidance for governing," meaning that the successes and failures of history could serve as lessons to strengthen rule. This is why the work was titled Zizhi Tongjian, or Comprehensive Mirror to Aid in Government.
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