Seeing Russia as a rival, Japan offered to recognize Russian dominance in Manchuria in exchange for recognition of Korea being within the Japanese sphere of influence. Russia refused and demanded the establishment of a neutral buffer zone between Russia and Japan in Korea north of the 39th parallel. The Japanese government perceived a threat to their plans for expansion into mainland Asia and chose to go to war. After negotiations broke down in 1904, the Japanese Navy opened hostilities in a surprise attack on by attacking the Russian Eastern Fleet at Port Arthur, China.