http://www.ageod-forum.com/showthread.php?t=17574
As stated in French on the thread above, it is currently way too difficult to successfully reassign units to detachments via drag-and-drop. The space to do this is so small, it becomes a work of precision to move each detachment and/or merge two differents detachments together.
While the tutorial states one only needs to drag the unit on the infantry sprite, in fact it must be dragged out, then moved in into the green horizontal scale below each infantry sprite, and sometimes even below, until the UI asks for the player to state in which detachment he or she wants to merge the unit.
Can something be done to improve the UI on this problem in the future, please?