gesture in a process of re-establishing diplomatic relations and as an earnest of future progress, some Joseon prisoners were released at Tsushima Island. In response, a small group of messengers under the leadership of Yu Jeong were sent to Kyoto to investigate further. With the assistance of Sō Yoshitomo, an audience with Tokugawa Ieyasu was arranged at Fushimi Castle in Kyoto. In 1604, Yu Jeong confirmed the Joseon interest in further developing relations; the Tokugawa shōgun reciprocated by releasing 1,390 prisoners-of-war. 15th–16th century diplomatic ventures In the 15th and 16th centuries, the Joseon court labeled four large-scale diplomatic missions to Japan as "communication envoys" or tongsinsa – in 1428, 1439, 1443 and 1590. In Japan's Muromachi period (1336–1573) and Azuchi–Momoyama period (1568–1603), these Joseon-Japanese diplomatic contacts were considered important events. {| class="wikitable" |- style="background:#efefef" ! scope="col" width=8% | Year ! scope="col" width=10% | Korean monarch ! scope="col" width=26% | Joseon chief envoy ! scope="col" width=10% | Japanese shōgun ! scope="col" width=48% | Official purpose |- align="center" |1428 |Sejong |Bak Seo-saeng |Ashikaga Yoshinori |align="left" | Condolences on the death of Yoshimochi, Congratulations on the succession of Yoshinori |- align="center" |1439 |Sejong |Go Deuk-jong |Ashikaga Yoshinori |align="left" | Neighborly relations, suppression of the waegu (wakō) |- align="center" |1443 |Sejong |Byeon Hyo-mun |Ashikaga Yoshimasa |align="left" | Condolences on the death of Yoshinori, congratulations on the succession of Yoshikatsu |- align="center" |1590 |Seonjo |Hwang Yun-gil<ref>Rutt, Richard et al. (2003). Korea: a Historical and Cultural Dictionary, p. 190.]</ref> |Toyotomi Hideyoshi |align="left" | Congratulations on the unification of Hideyoshi |- align="center" |} Hideyoshi's invasions Diplomacy was set aside in 1592 when Japanese armies invaded Joseon territory. The ruptured bilateral relations were not restored immediately after the death of Hideyoshi in 1598; but the invading forces gradually withdrew from occupied land on the Korean peninsula. 17th–19th century diplomatic ventures In the 17th, 18th and 19th centuries, the Joseon leaders sent twelve large-scale delegations to Japan, but not all were construed as "tongsinsa" envoys. The embassies consisted of 400 to 500 delegates; and these missions arguably contributed to the political and cultural development of Japan in addition to the range of ways in which bi-lateral relations were affected. The 1607, 1617 and 1624 delegations were explicitly identified by the Joseon court as "Reply and Prisoner Repatriation Envoys," which were construed as less formal than a tongsinsa or "communication envoy." The use of the term "tongsinsa" signified that relations