Well i probably have a slight different approach from all of my historical reading
From there i generally see 3 levels mentioned. The Strategic, the Operation and the tactical levels.
The Strategy is the overall plan. What to do and how to do it. IE, beat player X through a large assault through the left side of the map with a highly mobile force.
The Tactical level is how you handle each battle, how you attack, how you use the forces the best, defence and so on. Say a smoke screen before charging in, or having an artillery strike ready for when your tanks roll in to neutralize AT positions.
The Operational level is how you connect the two. Getting the right resources, but also connecting all the battles to the overall strategy. So that you do your best to invest more resources in west battles and to hold the territory there gain and so on. And not say, go willy nilly all over the map

Granted not really something you see much of in CoH or most RTS games. Although technically one could argue that most RTS games are in a sense more operational level games...
If you wanted

Which i don't atm. A bit late here. But thought i might as well mention it.