Wikipedia
The was a political doctrine in the Empire of Japan which stated that Southeast Asia and the Pacific Islands were Japan's sphere of interest and that the potential value to the Japanese Empire for economic and territorial expansion in those areas was greater than elsewhere.
This political doctrine was diametrically opposite that of the largely supported by the Imperial Japanese Army, which stated the same except with regards to Manchuria and Siberia. After the military setbacks at Nomonhan on Mongolian front, the Second Sino-Japanese War, and negative Western attitudes towards Japanese expansionist tendencies, Southern Expansion Doctrine superseded to procure colonial resources in South East Asia and neutralize the threat posed by Western military forces in the Pacific. The Army favored a "counterclockwise strike" while the Navy favored a "clockwise strike".