Nahm, Andrew C. (2005). A Panorama of 5000 Years: Korean History (Second revised ed.). Seoul: Hollym International Corporation. p. 18. ISBN093087868X. "China, which had been split into many states since the early 3rd century, was reunified by the Sui dynasty at the end of the 6th century. Soon after that, Sui China mobilized a large number of troops and launched war against Koguryŏ. However, the people of Koguryŏ were united and they were able to repel the Chinese aggressors. In 612, Sui troops invaded Korea again, but Koguryŏ forces fought bravely and destroyed Sui troops everywhere. General Ŭlchi Mundŏk of Koguryŏ completely wiped out some 300,000 Sui troops which came across the Yalu River in the battles near the Salsu River (now Ch'ŏngch'ŏn River) with his ingenious military tactics. Only 2,700 Sui troops were able to flee from Korea. The Sui dynasty, which wasted so much energy and manpower in aggressive wars against Koguryŏ, fell in 618."
