Dowager Zhang’s unofficial regency began when the Xuande emperor suddenly fell ill and died in 1435, creating a problem that had not yet occurred in the Ming. He had designated an heir apparent, his eldest son, Zhu Qizhen (Sun’s supposed son), but he was only eight years old. There was no precedent in the Ming for what to do in the case of a child emperor. The emperor gave vague instructions just before he died, which were that officials should guide the boy and in major matters seek assistance from his grandmother, Dowager Zhang. In the first tense moments, as the History of the Ming reports, rumors had it that a brother of Zhu Zhanji should rule, some saying that Zhang herself wished it. But in the end Zhang summoned the high ministers and, when they came, she wept and pointed to the young heir apparent, saying, “‘This is the new Son of Heaven.’ The rumors ceased immediately.

But it was still unclear what to do. The ministers requested that she “rule from behind the curtain,” the now accepted words to designate a woman ruling as regent. But she refused to do so because it “violated the ancestral mandate” established by Zhu Yuanzhang. As great empress dowager (taihuang taihou), she became informal regent instead and in this role saw to the care, training, and guidance of the new emperor, designating five ministers for him to listen to. She benefited from the fact that the ministers had served since Zhu Di’s time. […] Although her regency was never formalized, she was the power behind the throne from 1435 to her death in 1442, the third and last in a series of strong Ming empresses of a sort never quite seen again. A seventeenth-century historian called her a “Yao and Shun among women.”

Source: McMahon, Keith. Celestial Women: Imperial Wives and Concubines in China from Song to Qing. Rowman & Littlefield Publishers.