@Boyardee:
As the attacker, I’m I allowed to retreat form from a fight even before dice are rolled?
Does units must retreat to the same territory, even if they come from opposite side of the territory being attacked and wouldn’t normally had the right to move there?
No, I’m pretty sure you have to do at least one round of combat. This can be especially disasterous if an amphibious assault must retreat prior to unloading, as your non-amphib assault units are stuck for that first round. Plus, any amphibiously dropped units never have an option of retreating after they’ve been dropped off (which occurs after any naval battle in the associated seazone is complete). I think the only exception to this is that Subs CAN choose to immediately submerge prior to any full round of combat (attack/then defense), if no enemy destroyer is present.
Yes. It is possible to get units from one territory to another territory which they normally would not be able to reach through a retreat. An example: (on a revised map) German units from Norway could attack Karelia with units from West Russia and those units could then retreat to West Russia.