Movement is quite standard with units paying high movement costs unless they're ski-equipped Finns. Combat is based on odds and adjusted by terrain. Artillery can support combat in attack or defense within range or, alternatively, may barrage alone. Quite sensibly, the barrage is affected by terrain in the target hex and the number of units found there - the more the bloodier. Combat includes column shifts for armour which can be neutralised by having an anti-tank unit in the defending hex.
Rules also exist for tank fright, anti-tank gun capture and retreat before combat.
Engineers can build forts and roads, whilst the Finnish player can break units down into smaller components - useful for surrounding Soviets prior to combat for another combat shift. Combat results are retreats and step losses. Players may declare an assault to be a probe which halves losses to both sides but does not allow advance after combat. All in all, this is rather a good game on a fairly exotic topic. My only gripes would bc that the map is awful to look at and an apparent foul up between the Terrain Effects Chart and the rules.