After the Russo-Japanese War began, the 8th Division was mobilized in June 1904. It was initially earmarked for a projected Japanese invasion of Primorskaya Oblast on the Siberian mainland, but was sent as a reserve force for the Siege of Port Arthur instead after that plan was shelved.
As hostilities broke out between Russia and Japan in June 1904, the 8th Division was activated. Initially slated for a hypothetical Japanese assault on Primorskaya Oblast in Siberia, it was subsequently redirected as a holding force to bolster the Siege of Port Arthur after that operation was scrapped.