On April 13, 1592, the First Division of the Japanese invasion army, consisting of 7,000 men led by Konishi Yukinaga, left Tsushima in the morning, arriving at the Korean port city of Busan in the evening. Korean naval intelligence had detected the Japanese fleet, but Won Gyun, the Right Naval Commander of Gyeongsang, 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 the general did nothing about it.
Sō Yoshitoshi landed alone on the Busan shore to ask the Koreans for a safe passage to China for the last time; the Koreans refused, and Sō Yoshitoshi laid siege to the city.