and underestimation of the power of the arquebus greatly contributed to the failures of the Korean army early in the war. In April 1590, the Korean ambassadors including Hwang Yun-gil and Kim Saung-il left for Kyoto, where they waited for two months while Hideyoshi was finishing his campaign against the Hojo clan. Upon his return, they exchanged ceremonial gifts and delivered King Seonjo's letter to Hideyoshi. Hideyoshi mistakenly assumed that the Koreans had come to pay a tributary homage to Japan. For this reason the ambassadors were not given the formal treatment that was due to diplomatic representatives. In the end, the Korean ambassadors asked for Hideyoshi to write a reply to the Korean king, for which they waited 20 days at the port of Sakai. The letter, redrafted as requested by the ambassadors on the ground that it was too discourteous, invited Korea to submit to Japan and join in a war against China. Upon the ambassadors' return, the Joseon court held serious discussions concerning Japan's invitation; while Hwang Yun-gil reported conflicting estimates of Japanese military strength and intentions. They nonetheless pressed that a war was imminent. Kim Saung-il claimed that Hideyoshi's letter was nothing but a bluff. Moreover, the court, aware only that Japan was in turmoil with various clan armies fighting each other, substantially underrated the combined strength and abilities of many Japanese armies at the time. Some, including King Seonjo, argued that Ming should be informed about the dealings with Japan, as failure to do so could make Ming suspect Korea's allegiance, but the court finally concluded to wait further until the appropriate course of action became definite. In the end, Hideyoshi's diplomatic negotiations did not produce the desired result with Korea. The Joseon Court approached Japan as a country inferior to Korea, and saw itself as superior according to its favored position within the Chinese tributary system. It mistakenly evaluated Hideyoshi's threats of invasions to be no better than the common wokou Japanese pirate raids. The Korean court handed to Shigenobu and Genso, Hideyoshi's third embassy, King Seonjo's letter rebuking Hideyoshi for challenging the Chinese tributary system. Hideyoshi replied with another letter, but since it was not presented by a diplomat in person as expected by custom, the court ignored it. After this denial of his second request, Hideyoshi proceeded to launch his armies against Korea in 1592. Forces Japan The core of the Japanese