Some lament that China under Mr. Xi is returning ideologically to the Maoist era. But if the Red Aristocracy keeps rising, China’s politics may regress all the way back to medieval times.

Chinese society underwent radical structural changes between the Tang dynasty (618–907) and the Song dynasty (960–1279). Naito Konan, a prominent Japanese Sinologist, noted in the 1910s and 1920s that before the enlightened autocracy of the Song era, China had for many decades been ruled by an informally hereditary aristocracy whose emperors also filled top government posts and controlled the civil service examinations. The emperors created a closed, self-serving and rapacious elite — until the entire system suddenly collapsed.

Naito noted that for decades the dynasties remained stable even as emperors were often overthrown by other aristocrats. It was another historian, Nicolas Tackett, who recently explained why the aristocracy was finally done in, and why so quickly. After examining hundreds of epitaphs on graves from the ninth century, he concluded that the Tang empire was brought down by Huang Chao, a disgruntled salt-merchant-turned-rebel, who tapped popular discontent to wage a rebellion that swiftly turned into a blood bath — a class genocide that physically annihilated the entire medieval aristocratic class.