I was looking at this recent /r/pics post and started wondering what the plan was in the event that the Germans pushed back the invasion at some point after the beachhead was established. Was there a logistical plan in place to get all those vehicles, people, and materiel back on ships and back to England? Would it even have been possible with decent warning? At what point would they have decided to abandon the beachhead?
I don't know of any specific tactical planning regarding a rescue & retreat operation. However there is this note from Eisenhower, written when he gave the order to launch the operation despite bad weather forecasts: http://www.archives.gov/education/lessons/d-day-message/images/failure-message.gif
It says:
"Our landings in the Cherbourg-Havre area have failed to gain a satisfactory foothold and I have withdrawn the troops. My decision to attack at this time and place was based upon the best information available. The troops, the air and the navy did all that bravery and devotion to duly could do. If any blame or fault is attached to the attempt it is mine alone."
