It is impossible to have a retreat in S01, but that may not be the case in future seasons. Here is a quick review of Retreat and Build Rules so that you have them ahead of time.
Let me emphasize one rule on builds that catches new players: OCCUPYING SUPPLY CENTERS IN THE SPRING HAS NO EFFECT ON OWNERSHIP. You haven’t captured any SCs yet!
***** BASIC RULES FOR RETREATS *****
You cannot dislodge or cut support of your own units.
If there is a unit in a province where a standoff occurred, it is not dislodged.
Dislodged units may either retreat to an adjacent province (where it could move), or be destroyed (called “retreating off the board”).
You may not retreat to a province where there was a bounce or from where the attack came. If you submit an order to retreat to such a province, the retreating unit will be destroyed instead.
You may not retreat via a convoy.
If there is no legal retreat for a dislodged unit, it is automatically destroyed.
If two units try to retreat to the same province, they are both destroyed.
If a surrendered power has a dislodged unit, the unit will be destroyed.
If you don’t have any units to retreat, then the finalize button has no effect whatsoever. The step will process when the players that DO have orders for the step finalize or time expires. EXCEPTION: If the ONLY power with a retreat is a surrendered power, the turn will process when ANY power finalizes.
***** BASIC RULES FOR BUILDS *****
You gain control of supply centers by occupying them after Fall Retreats. They are yours until another power gains control of them. OCCUPYING SUPPLY CENTERS IN THE SPRING HAS NO EFFECT ON OWNERSHIP.
For every supply center you control, you may have one unit on the board. Adjustments to units are done once per year after Fall Retreats.
If you are short units, you may build new ones in unoccupied home centers. You may choose not to use all of the builds you are allowed – simply don’t enter the build order.
If you do not have as many unoccupied home centers as you have allowed builds, you must forego the excess builds.
If you have too many units, you MUST disband the excess.
If a required disband order is not entered, the unit farthest from a home supply center is disbanded. If units are equally far away, fleets are disbanded before armies, alphabetical order to break ties.
Just as with Retreats, if you have no adjustments, then the finalize button has no effect whatsoever. The step will process when the players that DO have orders for the step finalize or time expires. EXCEPTION: If the ONLY power with an adjustment is a surrendered power, the turn will process when ANY power finalizes.
***** OPTIONAL READING *****
“22 Rules To Help You Resolve Orders” is not the entire rulebook, but it is close and it is in a single page (Diplomacy really is a simple game and in many respects the rulebook is longer than it needs to be.) The list has been replicated in the Rules forum and when you have a rules question look here first:
The “common questions” link on that page also is just what it says. After you have checked out the rules and those summaries, if you still have a question, go ahead and post it in the Rules Questions forum and someone will usually answer your question within minutes.
Of course while the mentor game is going on, feel free to just ask me by PM. Remember to add your game number to the PM.