In the years after the Russo-Japanese War of 1904-5, strategic thinking in the Japanese military was largely divided between the priority of mainland Asia (see North Strike group), and the southern, Pacific Ocean direction.

The latter strategic planning for the Pacific was largely associated with the Imperial Japanese Navy. The South Strike group supporting strategic attention to the southern direction only received more general support after the experience of sharp land conflicts with the USSR in 1938 and 1938 persuaded the military as a whole that a land war for Eastern Asia was a difficult option.