"Corps Withdraw Order" Topic

In Empire V activation of a Withdraw order is automatic whereas in Empire III the order had to the activated. Am I correct?

In V it is called a break off. Not only is it not automatic, but it is activated with a -20 modifier and maximum possible is 80% regardless of any other modifiers or leader professional skill level. If it is successful, however, the opponent has a -20 modifier to reactivate attack.
Only automatic activations are Redeploy and Rest & Rally. And on first hour Defend and Garrison are also automatic.
Also if a corps commander or Imperial ADC is attached to ME it will be automatic unless there is a negative modifier (e.g. break off, reactivating attack after opponent breaks off, DUB cavalry activating attack).

Withdraw in V is automatic. Its a Corps Order not an ME Order tylamb. But in III ?

You are correct that the Corps order is activated immediately IF issued by Good or better army commander, but is delayed one hour for Mediocre or worse. This is considered easier than all other corps order so the delay in activation is reduced. All other orders have a longer delay. III and V are the same in this.
BUT if an ME is engaged it must activate a Break Off as stated above if it is to join in the withdrawal. An engaged ME can be left as a rear guard while the rest of the corps backs away. Maybe stand for an hour then try to break off or suave qui peut.