Tefal, this doesn't fit your requirements exactly and it's not a RTS by any stretch of the imagination, but it's a battle simulation involving battalion sized engagements with infantry, armour, air and artillery support. It can be real time or turn based and is based upon a fictional war in Syria in 2007. Can be played as the US Army, US Marines, British and Syrian forces - but it is not a walk in the park, and it is too hardcore for a lot of people. But it is considered a very accurate simulation and there is an awful lot of strategy involved too. You can progress in semi-dynamic campaigns and you have to manage your forces as applicable. There's a free demo out if you fancy a flutter.
http://www.battlefront.com/index.php?option=com_content&task=blogcategory&id=31&Itemid=252
There's also another game out by 1C and BFC which maybe more along the lines of what you fancy - Theatre of War 2. This is more of a RTS and is not as accurate as the above, but it is prettier, and plays pretty good too. You've got two theatres, Africa and Kursk in 1943.
You can also download a demo of this too.
http://www.battlefront.com/index.php?option=com_content&task=blogcategory&id=245&Itemid=383