Crossing Rivers and Mountain Ranges in GITM

In GITM, a unit moving strategically cannot cross a mountain range or river as part of its strategic movement when enemy combat units (non-HQ units) are present. It must first use tactical movement to cross to the other side of the mountain range or river. (If no enemy units are present, then strategic movement is permitted since the brigade will be able to cross the range/river automatically. Manual crossing is needed only in the presence of the enemy.)

Example: In a tactical map looking (in part) like this (assuming enemy combat units are present throughout):
 
  1 2 3 4 5 6
1            
2            
3          
4          
5            
6            

A unit at 4-2, on the north/east bank of the river, can march in seven directions: all but southwest. To march southwest it must first move to the south/west bank of the river (or to the ford; ford squares are on both banks). If it moves south or west, then it must remain on the same bank of the river it is currently on (north bank if it moves west; east bank if it moves south). Its entry square will be adjusted if necessary. If the unit moves northwest, north, northeast, east, or southeast, its movement is unconstrained by the river.

A unit at 3-5, on the south/west bank of the river, can march in three directions: west, southwest, and south. If it marches in the other five directions, it must first cross the river. If it moves south or west, it must remain on the same bank of the river (west bank if it moves south, south bank if it moves west) and its entry coordinate will be adjusted. If it moves southwest, its movement is unconstrained by the river.