When fighting on their own soil (the continent of Eurasia) the Russians are VERY TOUGH fighting men. As Japan found out in 1904 and 1905, then again in 1939 at Nomonhan; and the Germans found out in WW2.
Russia only lost two LARGE wars: Crimean War (1853-1856) and the Russo-Japanese War (1904-1905). And then only because they called it quits. The British and French got a run for their money at Crimea; and the Japanese were at the end of their rope in 1905. Had Russia persisted (and most of them wanted to) Japan would have run out of money, men, and warships...ultimately losing the war.