How you should march your troops up and engage in stituation five really depends on circumstances, although in all the cases I can think of, it is best to get your troops up as fast as you can. If they move to intercept while you are going up the hill, try to get 4 maneuvered so that it has hill advantage to D, if that cannot be done, at least get 4 to meet D so that neither unit have the hill advantage. If you are forced to meet D head-on w/ unit 4, take three up above it and have it fighting down the hill w/ unit 4 against D. Maneuver 1 and 2 so that they are near the fighting of 3, 4, and D. Ideally, as those units are getting engaged, 3 and 4 are finishing up and you can use advantage in morale and the hill and should handily win... If they do not move to intercept you as you march up the hill, try to maneuver to any hill advantage, which would probably amount to you getting up faster and cutting them off, which is what they should be trying to do to you. If it is a team game, and your teammates have decent situations, abandon the hill altogether and go 3-2 or whatever is the most favorable advantage numerically.

This however is largely in light of my MTW: VI experiences, so it may not apply as well to RTW.