Katsurayama Castle was a strategically vital Uesugi stronghold in the contested Shinano Province and, when it was isolated from reinforcements due to late snow in early 1557, the Takeda clan used this opportunity to attack it.

[2] Uesugi Kenshin consequently advanced into Shinano in order to halt Takeda Shingen's expansionism, resulting in a military conflict between the two that lasted years.

Instead of fighting the Uesugi along the Chikumagawa River as he had done so far, he would secure the mountain passes that went from the Kawanakajima plain west to Togakushi, from where he could circumvent and cut off the castles of Iiyama and Takanashi, and then strike into Echigo.

[9] The perfect opportunity to attack Katsurayama came in early 1557, when late snow[a] made the passes from Echigo into Shinano impassable and thus isolated the castle from Uesugi reinforcements.

This attack was effectively "a race against time", as the Uesugi would send reinforcements as soon as the thaw set in and the mountain passes were open again, and so the Takeda had to capture the castle before that could happen.

Historian Stephen Turnbull notes for example the Takeda samurai Chino Yugeinojo who fought in all the Battles of Kawanakajima and accompanying campaigns, collecting eight heads in total;[b] of these, he took four at Katsurayama alone.

Were the Takeda forces to learn of their low supply of clean drinking water, they would know that the garrison could not possibly hold out long enough for Uesugi reinforcements, providing a major advantage to the besiegers.

The torrent of rice looked like a waterfall from the Takeda lines, thus fooling the besiegers into thinking that the Katsurayama garrison had such ample water supplies that they could waste them in taunting displays.

With the majority of the castle garrison killed in combat, the wives, female attendants and children of the defenders committed mass suicide by jumping off the mountain cliffs.