Kenshin's adoption choices had been strategic. Uesugi Kagekatsu was his nephew -- the biological son of Nagao Masakage, Kenshin's elder brother -- and had grown up within the Uesugi inner circle at Kasugayama. Uesugi Kagetora was the biological son of Hojo Ujiyasu, lord of the powerful Odawara Hojo clan, adopted by Kenshin as part of a peace agreement. Kenshin apparently intended both men to share the inheritance, but that arrangement depended entirely on his authority to enforce it. The moment he died, the arrangement became meaningless. Neither heir carried the Uesugi name by birth. Both had external clan loyalties pulling at them. And both occupied fortified positions within the same castle complex.

Kagekatsu moved first. Immediately after Kenshin's death, he occupied the main keep of Kasugayama Castle and seized the family treasury, the gold storehouses, and the official documents that legitimized Uesugi authority. He sent letters to neighboring provinces proclaiming himself Kenshin's rightful successor. Kagetora, outmaneuvered within the castle walls, retreated roughly 500 meters west to the Otate -- the residence that Kenshin had built for Uesugi Norimasa, the former Kanto Kanrei. Otate was not a military fortification. It was a flat-style administrative residence in the castle town, lacking the weapons and supply stores needed for a prolonged defense. Kagetora's position was precarious from the start.

The succession crisis rippled outward across Japan's warring provinces. Takeda Katsuyori, son of Kenshin's legendary rival Takeda Shingen, initially attempted to mediate. When diplomacy failed, the Takeda backed Kagekatsu. The Hojo clan, Kagetora's birth family, rallied behind their blood. On April 23, 1578, Kagekatsu marched forces from Kasugayama to besiege Otate. The retainer clans split roughly in half: Honjo Shigenaga, the famous Naoe Kanetsugu, and Jojo Masashige sided with Kagekatsu, while Uesugi Norimasa, the Kitajo brothers, and Kawada Nagachika fought for Kagetora. The fighting ground on through the summer and into winter, draining both sides.

By the winter of 1578-1579, Kagetora's position had collapsed. Key generals defected or fell, and supplies at the poorly fortified Otate ran out. Kagetora abandoned the residence and fled toward the border with Shinano Province, making for Samegao Castle. He never reached safety. Betrayed by the castle's commander, Kagetora took his own life by seppuku at Samegao, ending the succession war. Kagekatsu claimed the full Uesugi inheritance, but it was a hollow victory. The months of internal conflict had shattered clan unity and exhausted military resources at the worst possible time -- Oda Nobunaga's forces were pressing from the west, and the Hojo remained hostile on the eastern border. The Uesugi would never again command the power they held under Kenshin. The Dragon of Echigo's legacy survived, but the fire behind it had dimmed.