the draft. All males had to enter military service to be trained and familiarized with weapons. It was also around this time that the military officer and military scholar Han Gyo (한교) wrote the martial arts manual Muyejebo, based on the book Jixiao Xinshu by the famous Chinese general Qi Jiguang. Imjin War: Japanese first invasion (1592–1593) Initial attacks Landing of a Japanese army On May 23, 1592, the First Division of the Japanese invasion army, consisting of 7,000 men led by Konishi Yukinaga, left Tsushima in the morning, and arrived outside the port city of Busan in the evening. Korean naval intelligence had detected the Japanese fleet, but Won Gyun, the Right Naval Commander of Gyeongsang Province, misidentified the fleet as trading vessels on a mission. A later report of the arrival of an additional 100 Japanese vessels raised his suspicions, but he did nothing about it. Sō Yoshitoshi landed alone on the Busan shore to ask the Koreans for safe passage to China one last time; the Koreans refused as they had previously done, and Sō Yoshitoshi laid siege to the city. Konishi Yukinaga attacked the nearby fort of Dadaejin the next morning. Japanese accounts claim that the battles resulted in the complete annihilation of Korean forces (one claims 8,500 deaths, and another, 30,000 heads), while a Korean account claims that the Japanese themselves took significant losses before sacking the city of Busan. Jeong Bal, the Korean commander at Busan, was killed by a Japanese bullet, and with his death, Korean morale collapsed. In the meantime Konishi took the fort of Dadaejin, where under heavy volleys of supporting fire, the Japanese were able to place ladders against the walls, and took the fort. Konishi ordered that no prisoners be taken, and the entire garrison was massacred. Konishi and the First Division then turned north, marching to take Hanseong. The disciplined Japanese brought down a rain of bullets that was lethal to anyone not taking cover. On the morning of May 25, 1592, the First Division arrived at the Dongnae Fortress. Konishi sent a message to Song Sang-hyeon, the commander of the fortress, explaining to him that his objective was the conquest of China and if the Koreans would just submit, their lives would be spared. Song replied "It is easy for me to die, but difficult to let you pass", which led Konishi to order that no prisoners