Withdraw towards battlezone in mirror image (4,2,5)
I believe the answer is:
back to front
If this is the answer I cannot explain how the clue works.
Can you help me to learn more?
(Other definitions for back to front that I've seen before include "rejoin colleagues in the trenches?" , "In disorder" , "may be reversed" , "perverted" , "like soldiers returned from leave" .)