In Company of Heroes originally the two teams were America and Germany. Now Russia has replaced the American team and taken on just about the same structure.
As Russia you need Pioneers to build a base for each kind of unit, then you can immedately start building the units when you have enough resources. Germany is still works as before, requiring only that you escalate the battle stage to unlock units, unlocking stronger types with each escalation.
Relic have brought some exciting features into the fray this time round that add more tactical possibilities through realistic thinking. These include the player's field of vision being directly affected by the vision of their units and the cold winter bringing new challenges to the table. They're pretty advanced, not just for their own games but for any RTS.
If you have troops taking cover behind a wall that's taller than them you are completely blind to what's directly on the other side. If a unit is approaching a corner that they can't see over you'll notice the fog of war clear around it as they advance, constantly keeping with their line of sight.
Some of the tanks even have abilities to alter their line of sight in various ways. With one you can have the driver look directly out of the front, resulting in a narrower but longer range of vision. With another you can have the gunner stick his head out of the turret, letting you see further all around but making the main gun unavailable.
Even grenades and RPGs can bring down walls and buildings. Explosions of any size can leave potholes in the terrain itself, making it increasingly difficult to traverse as the damage adds up throughout the battle. The most spectacular use of this is in the winter version of the maps where there are frozen lakes and rivers that are so deep you wouldn't be able to cross them on the spring version of the map.
The more weight you're carrying across ice, the easier it is for the enemy to smash it and sink you. If you have a tank wandering across, all it takes is a grenade from the enemy to bury it along with anything directly next to it. Getting around through these shortcuts bring a huge risk = reward factor.
Cold tech also brings weather and unit temperature. As if to take camping from gamespeak to a whole new level your Pioneers are able to build campfires just about anywhere. These are mostly useful every so often when the whole map becomes engulfed in a blizzard. Out in the cold your troops' temperature will drop, slowing them right down at first. If you don't get them inside a vehicle or near a campfire they'll start to suffer. One by one they'll freeze to death and before too long you can lose entire units.
Some of the units have had some improvements, like Conscripts. Poorly trained soldiers with not much firepower and a high chance of fleeing tough situations. On their own they're not very effective compared to heavier or better trained units but they can merge with any other damaged infantry unit to make them whole again. Thanks to this you don't need to keep sending loads of the same unit as backup, you only need a few and then keep making cheap Conscripts to replenish your numbers.
