the army you deploy to has to have an 'order' like a front (or part of it), a battleplan or a fallback line. And then you assign them basically to the order. 
When they're ready to deploy or you force deploy them, they will do in the province you selected, and move to (their spot) on the order you assigned them to.
When they're ready to deploy or you force deploy them, they will do in the province you selected, and move to (their spot) on the order you assigned them to.