Hōjō side, and sent messages to the Uesugi. He became one of Uesugi's generals, and helped the Uesugi drive out the Hōjō forces. Kenshin seized total control of Kōzuke, installed Nagano Narimasa as governor in Minowa Castle, and returned to his base in Echigo. Kamiizumi joined Nagano's service, and quickly became one of the "Sixteen Spears of Nagano House". In particular he distinguished himself when Nagano attacked Yamanaka Castle, and became known as "the best spearsman of Kōzuke." Nagano held off attacks from Takeda Shingen for seven years from Minowa Castle, but he died in 1561. His heir, Ukyō-no-shin Narimori, was only 16 years old, so Nagano’s death was kept secret as long as possible. Shingen eventually found out, and in 1563 (some sources suggest 1566), he invaded western Kōzuke with a force of over 10,000 Kai soldiers. The Kōyō Gunkan dates the invasion to 1563, while the records of Chōnenji, the temple where Nagano was buried, dates it to 1566. Minowa Castle was completely surrounded and besieged. Narimori killed himself on February 22, morale fell, and the castle followed on the 28th. Kamiizumi fought his way out of the castle, and escaped to eastern Kōzuke, where he joined with Kiryū Ōinosuke Naotsuna. But Naotsuna died soon thereafter and his son Matajirō Shigetsuna took over. With this, Kamiizumi returned to Minowa Castle. It is not known why. One story is that he returned because of many friends still at the castle, and there he joined the service of Naitō Shūri-no-kami, the governor appointed by Shingen. Or, another story is that, impressed by Kamiizumi's valor, Shingen invited him to join the Takeda side after Minowa Castle fell. How exactly it came about is not clear, but what is clear is that Kamiizumi became a minor official to the Takeda clan. A common story is that in recognition of his tremendous ability in defense of the castle, Takeda Shingen allowed Kamiizumi the use of the 信 character (read as either “shin” in “Shingen”, or “nobu” as in “Harunobu”) in his name, and thereafter Kamiizumi was known as Nobutsuna. However, in the license of transmission given to Yagyū Munetoshi in 1565, Kamiizumi signs it as “Kamiizumi Ise-no-kami Fujiwara-no-Hidetsuna”, and in the scrolls given to Munetoshi the following year he signs “Kamiizumi Ise-no-kami Fujiwara-no-Nobutsuna (上泉伊勢守藤原信綱).” If Minowa Castle fell in 1563, Kamiizumi was still using “Hidetsuna” two years later. If it fell in 1566,