Empress Cao (曹皇后, personal name unknown) was the wife of Dou Jiande, an agrarian rebel leader who claimed the title of Prince of Xia at the end of the Chinese Sui Dynasty. Nothing is known about her personal background. She was said to be frugal in her living, as even after Dou conquered modern Hebei and had substantial holdings, she had no decoration on her clothing, and only had less than 10 maids attending her. After Dou defeated and killed Yuwen Huaji, who carried a large number of ladies in waiting of Emperor Yang of Sui in his possession, Dou disbanded the ladies in waiting. (Novels fictionalizing the era generally attribute Dou's disbanding of the ladies in waiting to his love for her and her jealousy, but nothing is recorded in history suggesting that she was, in fact, jealous.) Dou himself only claimed the title of prince, not emperor, but after he heard in 619 that Wang Shichong had deposed the last emperor of Sui, Yang Tong, and declared himself the Emperor of Zheng, Dou cut off Wang and began to take on imperial style in his ceremonies, including referring to his orders as imperial edicts. It was likely that it was at this time that he let her take on the title of empress. In 621, with Wang's Zheng state under attack by the Tang Dynasty general Li Shimin (the later Emperor Taizong), Wang sought aid from Dou. Dou, believing that if Li were able to conquer Zheng, that his Xia state would be next, decided to go to Wang's aid. As he approached Luoyang, his strategist Ling Jing (凌敬) suggested that instead of heading to Zheng's capital Luoyang, which Li was sieging, that he attack Tang's Fen (汾州, roughly modern Lüliang, Shanxi) and Jin (晉州, roughly modern Linfen, Shanxi) prefectures and be poised to further attack Tang's capital Chang'an in order to seize Tang territory as well as force Li to give up the siege on Luoyang. However, Wang's emissaries Wang Wan (王琬) and Zhangsun Anshi (長孫安世) persuaded Dou that Luoyang was about to fall and needed his aid immediately, and so Dou headed for Luoyang. When Empress Cao heard this, she tried to persuade Dou to accept Ling's plan, stating: The strategy of the Secretary General [(i.e., Ling)] must be accepted, and I do not understand why Your Royal Highness would not accept it. Your Royal Highness