The Russo Japanese war provided clear portents of what was to come in warfare in the early 20th century, if only those responsible for determining doctrine had paid more attention. Given the scale of some of the battles, the conflict lends itself to game play using the Great War Spearhead rules system. Here are some links to some resources that you may find useful if you should like to give it a try.
Suggested Great War Spearhead rules amendments for game play
Machine guns in the Russo-Japanese War (I think this information was provided by Jeff Lesler, but have lost the attribution .. apologies to Jeff)
MODERN TENDENCIES IN STRATEGY AND TACTICS AS SHOWN IN CAMPAIGNS IN THE FAR EAST, By Lieutenant Colonel Yoda, Imperial Japanese Army (again I have lost the attribution, but I think this came from the old Russo Japanese War Research Society web site)
NOTES UPON COMPANY AND BATTALION TACTICS AND THE EMPLOYMENT OF ARTILLERY IN BATTLE BASED ON THE EXPERIENCES OF THE RUSSO-JAPANESE WAR OF 1904-5, By Captain A. Degtyarev [1] (Again I think this came form the Russo Japanese War Research Society web site.)
Nanshan Defences - some notes from Jeff Lesler
Andrew's Wargaming page features some very cool material on wargaming the RJW in 20mm