I am pretty sure that only the space marines can do that. In regards to them, the rule is on page 51 of the C:SM. Otherwise, I am pretty sure you are out of luck.Is there a rule or a reference to making a unit voluntarily fall back from an assault? For example against a unit that you cant kill, can you voluntarily get away from that unit?
Hit and run is different from fall back. It is a USR that uses an initiative test to allow a unit to break away and move 3d6 inches in any direction ignoring the enemy units and doesn't allow a sweeping advance.What about Hit and Run? doesn't that allow you to escape in good order!
It doesn't change the chapter tactics, but as long as he is on the table, you can pass or fail as you see fit. So, for all intents and purposes, that is correct.As I recall Combat Tactics lets you Fail any Morale test you fancy but Marneus Lets you choose to pass or fail any Morale test.