The Imperial Navy began to plan for the offensive against the Soviet Union when the Second Sino-Japanese War was drawn into a quagmire and Changkufeng Incident and Nomonhan Incident occurred one after the other.
日華事変の泥沼化に加え、張鼓峰事件とノモンハン事件が相次いで勃発したことから、海軍はソビエト連邦に対する迎撃策を講じることになった。