The objectives should clearly explain what to do here. Move quick to clear your starting areas and so to receive more reinforcements. The faster you position your troops, the easier the map becomes. The enemy is in full retreat and in case one enemy/AI unit reaches the end of the road in the west, you will lose, so set up an ambush on the 'pimple' and a roadblock west of it, but also watch your flank east of the 'pimple'!

Try taking positions like this:

Prepare for a dull fight. Some enemy units will surrender and head south to become imprisoned. When the enemy retreat has come to an halt, go north and take out whatever is needed to complete the mission.