Social wars unit warehouse
Is there a unit warehouse in social wars if not there should be
-Kill the units off and use the hospital as such.
-You can also build bunkers and put some units in there, but not all of them.
-A transportation truck is one of the rewards durring early PvP, it can be used to store some units (I think, I haven't tested it because I use the hospital) unit cannot attack from this truck though.
What ever method you choose, you'll lose the leveling of your units regardless.