Throughout the 1930s, the Soviet Far Eastern Army skirmished with the Kwantung Army along their borders in Siberia, Mongolia, and even Korea. The Japanese Army always saw the Soviet Union as its prime enemy, and looked north to annex Siberia for the Emperor. However, all knew that dominance of the provinces wouldn't be possible unless they accomplished two things: cut the Trans-Siberian railroad, and; neutralize Vladivostok, the most important port city for the Soviet Union on the Pacific. If these two objectives could be met, Japan would dominate Siberia without Russian interference.