This tactic allows you to create a forward makeshift base where units can reinforce and heal off.
For this you shall require: A Major
A Military Ambulance
Very quick and easy. Just behind your front line place your major in cover and set him as a 'Retreat point', this means that any retreating units shall fall back to the Major if he is closer to them, which he will be. You then place the ambulance next to the Major. Retreat a damaged unit back to the Major and then use the ambulance to reinforce them, if they need healing then disembark the Medics and then click 'First aid', this will heal the units.
The major can use his special abilities such as the combined artillery to support the front line troops.
Feedback would be appreciated, thanks!