I got the game on Monday and am really enjoying it. I've read the manual and played through the tutorials but as I begin my march into Austria in the 1805 scenario I have a small problem:
In the Northern Italy area are three stacks. The Army of Italy, another large stack in the same region and a small stack over to the West. The three star general of the Army of Italy has the HQ attached but I cannot add the other stacks as corps. What am I doing wrong?

Any help is greatly appreciated