Background
The San Guo period was one of the highest-frequency plague eras in Chinese history. Beginning with the reign of Emperor Ling of the Eastern Han, large-scale epidemics repeatedly struck the Yellow River basin — "great plagues" are recorded multiple times from the Yanxi era (158–167) through the Guanghe era (178–184), and the mass following of the Huangjinqiyi itself was closely connected to Zhang Jiao's "Way of Great Peace" attracting vast numbers of epidemic-stricken refugees with its talismanic water cures. The plagues did not stop with the Jian'an years — the Jian'an era alone records major epidemic events in years nine (204), thirteen (208), twenty-two (217), and twenty-four (219). The epidemic of the winter of the twenty-second year of Jian'an (217) broke out around the time Cao Cao was preparing his southern campaign against Sun Quan; it originated in the north and spread rapidly with armies and refugees, becoming the largest and most deeply affecting epidemic outbreak of the late Han.
Course of Events
In the winter of 217, the epidemic first erupted in the northern heartland — Yecheng and its surroundings — then spread into the southern military camps with Cao Cao's southbound campaign forces. That year Cao Cao's troops were concentrating at the Juchao line in preparation for attacking Sun Quan; the epidemic ran rampant through the army, and Wang Can, who had marched south with the forces, contracted the disease and died in camp at the age of forty-one. Back in the north, Chen Lin, Xu Gan, Ying Chang, and Liu Zhen died in succession around Yecheng and its vicinity. Sima Lang, then serving as Governor of Yanzhou, also died that year after contracting the epidemic while inspecting troops, aged only forty-seven. When Cao Cao at the front learned the full severity of the epidemic in the rear and in the army, he was compelled to revise his military plans and redirect attention toward internal governance and social relief — he subsequently issued an edict providing lifetime grain stipends to widows over seventy with no sons, orphans under twelve with no brothers, and disabled persons without family or property. This edict has been regarded by historians as a pioneering act of state social welfare at the Han-Wei transition.
Outcome
From a demographic perspective, the death toll of the twenty-second-year Jian'an epidemic cannot be precisely reconstructed, but from Zhang Zhongjing's preface to the Shanhan Lun — where he states that "since the beginning of the Jian'an reign period, not yet ten years have passed, and yet two-thirds have died, seven-tenths of them from cold damage diseases" — even allowing for some exaggeration, this implies a mortality rate in the 30–60% range for the contemporary northern population. At the elite level, this epidemic directly destroyed the Jian'an literary community — five of the remaining Seven Masters perished in the same year. The scale of this cultural loss is exceedingly rare in Chinese literary history, equivalent to a "generational erasure." Cao Pi's letter to Wu Zhi the following year (218) — "Last year's epidemic took many of those close to me as its victims. Xu, Chen, Ying, and Liu all departed at once — can the pain be put into words?" — is the most direct firsthand testimony to this literary catastrophe.
Impact
The impact of the twenty-second-year Jian'an epidemic extended across three levels. The first was the literary level: after the Jian'an Seven Masters perished, the brothers Cao Pi and Cao Zhi became the practical center of the Ye literary circle, and literary criticism and theory shifted from practice to theory — the tradition of literary self-consciousness running through Cao Pi's "Discourse on Literature" in the Dianlun and Lu Ji's "Rhapsody on Literature" was directly connected to the atmosphere of reflection following the Seven Masters' deaths. The second was the medical level: stimulated repeatedly by the late-Han plagues, Zhang Zhongjing completed the Shanghan Zabing Lun, establishing the systematic framework of Chinese medicine for externally-contracted febrile diseases. Cao Zhi's "On the Epidemic Qi" placed side by side the superstitious view of "epidemics as the work of ghosts and spirits" and the rationalist view of "yin and yang out of position, cold and heat in the wrong season" — an important document in the early history of medical thought. The third was the political level: the epidemic of the twenty-fourth year of Jian'an (219) struck Cao Cao's front line in Nanyang once more, and coincided in time and geography with Guan Yu's victory of Shuiyanqijun — Cao Cao's forces, already severely depleted by disease, faced a sudden assault when Guan Yu exploited the Hanshui River's flooding, which is how such enormous results were achieved. In other words, the epidemic of 217 was not an isolated event but the most lethal link in a chain of more than thirty years of plagues through the late Han, whose shadow extended across the entire process of the San Guo configuration taking shape. Seen from this angle, the collective decimation of the Jian'an Seven Masters was simultaneously a literary event and a multi-dimensional convergence of political, military, and demographic history — and that is the fundamental reason later historians treat the Jiananershierniandayi as one of the turning points of the Han-Wei transition.