By mid-1935, Aizawa despised Major General Tetsuzan Nagata, the de facto leader of the Tōseiha, whose ideas earned him the violent animosity as "chief villain" of the Kōdōha.

Nagata's national mobilization strategy of preparing both the military and civilian economy for total war offended the Kōdōha, who perceived it as collusion with corrupt party politics and the zaibatsu.

In July 1935, Nagata's political manoeuvres led to the forced retirement of Jinzaburō Masaki, the Inspector-General of Military Training, who was a leading member of Kōdōha and Aizawa's friend.

Aizawa entered Nagata's office in Tokyo and cut him down with his sword, making no attempt to resist arrest by military police and reportedly said that he "was in an absolute sphere, so there was neither affirmation nor negation, neither good nor evil".

On 3 July 1936, Aizawa was executed by firing squad after a high-profile court martial trial held by the IJA 1st Division.