the Yellow River and connecting the Yellow River with the Huai River, as well as to rebuild the Han Canal (), connecting the Huai River and the Yangtze River. The two canals, which would eventually become parts of the Grand Canal of China, were said to be constructed within five months, but at substantial cost of life—40% to 50% of the men employed. Emperor Yang also ordered that some 40 secondary palaces be built around the empire, so that he could visit the various provinces, arguing that he needed to do so to see the conditions of the empire so that he could govern effectively. In fall 605, after the completion of the Tongji and Han Canals, Emperor Yang carried out the first of 11 (counting military campaigns) tours that he would eventually undertake of various parts of the empire, going to Jiangdu—the capital of Yang Province, where he had been commandant previously—on an imperial ship that was said to be sufficiently large and luxurious to serve as floating palaces. Also in 605, when Khitan tribes attacked Ying Province (營州, roughly modern Zhaoyang, Liaoning), Emperor Yang had the official Wei Yunqi () requisition Tujue troops under Ashina Rangan to attack Khitan. The Khitan forces were caught by surprise and defeated. In summer 606, Yang Zhao the Crown Prince became ill while visiting Luoyang, and soon died. Emperor Yang would not create another crown prince for the rest of his reign, creating Yang Zhao's sons Yang Tan (), Yang Tong, and Yang You imperial princes, while initially apparently tacitly considering his second son, Yang Jian the Prince of Qi (note different character than Emperor Wen) the de facto successor, leaving Yang Jian in charge of Luoyang whenever he would be away from Luoyang. Yang Su, whom Emperor Yang pretended to respect but actually feared, also died in summer 606. Also in 606, Emperor Yang ordered that two massive food storages—the Luokou Storage () and the Huiluo Storage () – be constructed near Luoyang. In spring 607, Ashina Rangan visited Emperor Yang at Luoyang. Also in spring 607, at the instigation of Yuwen Shu, Emperor Yang had Yang Yong's eight sons put to death. In summer 607, Emperor Yang abolished provinces and changed them to commanderies. At the same time, he reorganized his father's governmental system of having five main bureaus, keeping four of the main bureaus—the executive bureau (尚書省, Shangshu Sheng),