About this time the Sui Emperor had business in the north. The Tol-gwŭl tribe needed chastisement. When the Chinese forces entered the chief town of the humbled tribe they found a Ko-gu-ryŭ emissary there. This fed the Emperor’s suspicions for it looked as if Ko-gu-ryŭ were preparing a league of the wild tribes for the purpose of conquest. He therefore sent to Ko-gu-ryŭ saying “The king should not be afraid of me. Let him come himself and do obeisance. If not, I shall send and destroy him.” We may well imagine that this pressing invitation was declined by the king. The last year of the sixth century witnessed the compilation of the first great history of Ko-gu-ryŭ, in 100 volumes. It was named the Yu-geui or “Record of Remembrance.” It took China some years to get ready for the carrying out of her plan, but at last in 612 began one of the mightiest military movements in history. China massed upon the western bank of the Liao River an army of 1,130,000 men. There were forty regiments of cavalry and eighty of infantry. The army was divided into twenty-four battalions, marching with an interval of forty _li_ between each, so that the entire army stretched for 960 _li_ or 320 miles along the road. Eighty _li_ in the rear came the Emperor with his body-guard. When this enormous army reached the banks of the Liao they beheld on the farther bank the soldiers of Ko-gu-ryŭ. Nothing can better prove the hardihood of the Ko-gu-ryŭ soldiery than that, when they saw this well-nigh innumerable host approach, they dared to dispute the crossing of the river. The Chinese army was composed of Chinese regulars and of allies from twenty-four of their dependencies whose names are given as follows. Nu-bang, Chang-jam, Myŭng-hă, Kă-ma, Kön-an, Nam-so, Yo-dong, Hyŭn-do, Pu-yŭ, Nang-nang, Ok-jŭ, Chŭm-sŭn, Ham-ja, Hon-mi, Im-dun, Hu-sŭng, Che-hă, Tap-don, Suk-sin, Kal-sŭk, Tong-i, Tă-bang and Yang-p’yŭng. One would suppose from this long list that there could be few left to act as allies to Ko-gu-ryŭ, but when we remember that the Mal-gal group of tribes was by far the most powerful and warlike of all the northern hordes we will see that Ko-gu-ryŭ was not without allies. In addition to this, Ko-gu-ryŭ had two important factors in her favor; in summer the rains made the greater part of Liao-tung impassable either for advance or retreat, and in winter the severity of the weather rendered military operations next to impossible. Only two courses were therefore open to an invading army; either it must make a quick dash into Ko-gu-ryŭ in the spring or autumn and retire before the summer rains or winter storms, or else it must be prepared to go into camp and spend the inclement season in an enemy’s country, cut off from its base of supplies. It was in the spring that this invasion took place and the Emperor was determined to carry it through to a finish in spite of summer rains or winter storms.