Toy Soldiers a gem of a game for RTS fans like me!!!
The difficulty of normal is just right, and hard is definitely harder but not TOO hard. There is also an elite mode which brings you to a point where ONLY the vehicle/gun you are using is doing damage. This is tough!!! It pays to know the level and where the enemies are coming from.
Oh, I almost forgot about vehicles! Aside from the gunpower at your disposal (all of which you can control if you want to), you are also given vehicles on some levels. You can control different types of tanks, bomber planes, and fighter planes. Oh yes, you are also in World War I time periods, so it's a biplane!!!