Since the Russo-Japanese War, Japanese army war plans had focused on defeating Russia in an anticipated war to end all wars for Siberia east of Lake Baikal. Army warnings about the Russian threat assumed a shrill tone after the Russian Revolution when the simple problem of Russian imperialism acquired an ideological dimension with the admixture of communism. These fears then became chronic with the post–World War I economic depression in Japan followed by the global Great Depression, which together made communism increasingly attractive to Japanese labor leaders and rank and file.

Russian revolutionaries deployed cadres around the globe to spread communism and made clear their goal not only to overturn the global order, but also to overturn the domestic orders within each country with social revolutions for all. Political and economic elites knew what to expect on the basis of the Russian Revolution – a classwide death sentence. Previously, the Russian threat to Japan had been strictly external in terms of territorial expansion abroad, but with the spread of communism, it became a domestic threat that sounded internal alarm bells throughout the Japanese government, and most particularly at army headquarters.