Emperor Taizong of Tang

He came to the throne by killing his brothers and became the model Chinese emperor anyway. The twenty-three years of the Zhenguan reign — an administration that tolerated being contradicted, a legal code copied across East Asia, and a frontier pushed deep into the steppe — were held up as the standard for the next twelve centuries.

What the histories dwell on is not the conquests but the tone of the government: the remonstrance officials, Wei Zheng above all, whose job was to tell the emperor he was wrong, and an emperor who made a public performance of listening. The Zhenguan Zhengyao, a digest of those arguments, was still required reading for rulers in Japan and Korea a thousand years later.

Abroad he broke the Eastern Turkic Khaganate in 630 and was acclaimed Heavenly Khagan by the steppe confederations — the first Chinese emperor to hold both titles. At home the census recovered, the granaries filled, and the capital became the largest city in the world.

Empress Zhangsun, whom he had married at thirteen, argued against every attempt to promote her own family and died in 636 at thirty-six. He never appointed another empress. One of the junior consorts of his last years was a girl named Wu — Xiang Li paints her too, five reigns later, as the only woman to rule China in her own name.