The Longest Canal in the Ancient World-Ending
In 612, despite his officials' counsel, Emperor Yang Di assembled an army of about 2 million strong, Placing himself in command, and launched a great campaign against the Gaoli (northern Korean Peninsula). At Pyongyang, Emperor Yang Di laid siege to the city but could not capture it. His expedition was too far extended into the foreign land and his supply line failed, notwithstanding the 2 million workforce taking care of it. Seeing no hope to break into the city, the emperor ordered his men to retreat. The Gaoli army gave chase and crushed the Chinese forces, killing their commander-in-chief Of the 300,000 frontier soldiers in the emperor's expedition, only 2,700 came back alive.
In 613 the emperor's second personally led campaign against Gaoli again ended fruitlessly. In 614 he prepared for a third one. After prolonged bitter warfare with success for either side nowhere in sight, the emperor agreed to make peace when the King of Gaoli offered to surrender. With a large percentage of the labor force recruited for the three consecutive campaigns, farmlands had been left untended, and the country's overall economy had weakened.
From 611 to 616, hungry peasants revolted, followed by landlords and military leaders who saw that the Sui Dynasty was doomed. In 617 the Governor of Taiyuan, LiYuan, took Chang'an while Emperor Yang Di was away on a tour in the south. His royal guards were tired of their emperor's roving ways, and desired to return to Chang'an where their families were. The emperor felt desperate, knowing that his fate was sealed. He could not sleep unless his chambermaids patted him and comforted him like nursemaids do for small children. And when he did fall asleep, he slept with disturbed dreams and nightmares, which frequently woke him up.
In 618, taking advantage of the soldiers' discontent and homesickness, a general named Yuwen Huaji mutinied, and captured Emperor Yang Di. He had the emperor strangled to death. The emperor died believing himself to be innocent. He was given the posthumous title "Yang," which meant "indulgence in sensual pleasures and neglect of duty," a rather deserving comment on him as an emperor. Things for him seemed to have come around full circle, because that was the exact posthumous title he had given the last king of the Chen Dynasty, whom his father had conquered.