Naoe Kanetsugu
Mogami Yoshimori's eldest son, Mogami Yoshiaki fought many battle against various cadet branches of his own clan as well as the local warlords of many strongholds across Dewa Province from his base at Yamagata, with the Date clan sometimes assisting, but more often hindering his efforts to unit the province. However, following an invasion by Uesugi Kagekatsu, who captured the Shōnai region, Yoshiaki was forced to submit to Toyotomi Hideyoshi. Yoshiaki rebuilt Yamagata Castle in 1592, adding a second bailey and third bailey, and a number of two-story and three-story "yagura" watchtowers. The castle never had a "tenshu". He also laid out the "jōkamachi" for what later became the city of Yamagata. However, his relations with the Toyotomi were always strained, as the Toyotomi favored the Uesugi clan, and Mogami Yoshiaki's daughter Komahime was killed by Hideyoshi when he purged Toyotomi Hidetsugu and his household. At the time of the Sekigahara campaign, Mogami Yoshiaki sided with Tokugawa Ieyasu. The forces of the Uesugi clan under Naoe Kanetsugu invaded the Yonezawa basin. Despite being severely outnumbered, the Mogami were able to repulse the invasion. The Mogami were rewarded after the establishment of the Tokugawa shogunate with an increase in territory to 570,000 "koku" with the recovery of the Shōnai region. This led to a further expansion of Yamagata Castle.