These changes and adoptions into Sengoku era Japanese warfare made themselves present during the Japanese invasions of Korea of 1592-1598 after Toyotomi Hideyoshi had unified Japan. Early success in the first incursion during May 1592 into Korea was attributed to the varied small arms and tactics of the Japanese forces, allowing them to make and defend early footholds into the Korean peninsula. However, after the Koreans had allied themselves with Ming China, they gained access to better artillery with greater range and destructive power than their Japanese equivalents. Finally, the Korean navy under the command of Yi Sun-sin had utilized the superior, cannon-armed navy of the Korean-Ming alliance against the Japanese maritime supply lines, eventually leading to a shortage of supplies and Japanese losses on the mainland. Japan was driven off their last stronghold in Seoul in May 1594, and subsequent ventures 1597 would not come close to the success of the first, as the Korean-Ming alliance had developed countermeasures and equivalent small arms to Japanese equivalents.