The roots of anti-Soviet sentiment in Imperial Japan existed before the foundation of the Soviet Union itself. Eager to limit tsarist influence in East Asia after the Russo-Japanese War (1904–1905) and then to contain the spread of Bolshevism during the Russian Civil War, the Japanese deployed some 70,000 troops into Siberia from 1918 to 1922 as part of their intervention on the side of the White Movement, occupying Vladivostok and other key points east of Lake Baikal. After the international withdrawal from Russian territory and the establishment of the Soviet regime, the Imperial Japanese Army, mindful of the Soviets' potential as a military power and in keeping with the convention of Russia as a traditional enemy, made contingency plans for a future war. Initially defensive in nature, they envisioned an invasion by the Red Army into Chinese territory that would then be parried by a Japanese counterattack from Korea, with the decisive battlefield being southern Manchuria. After the Japanese invaded Manchuria in 1931, Japanese and Soviet troops found themselves facing one another along a border thousands of kilometers in length. To protect the puppet state of Manchukuo and to seize the initiative early against the Red Army, the IJA adopted a policy of halting any Soviet advance along the border and fighting the greater part of the war in Siberia, an "epoch-making change" in Japanese strategic thought. The transition from the strategic defensive to the strategic offensive would not be reversed until 1945, when Japan was facing disaster during the Pacific War. Moreover, Japanese plans progressively increased in scope from relatively small-scale operations to gigantic multistage campaigns, which envisioned seizing virtually the entire Soviet Far East as far as Lake Baikal.