Question: A planet, owned by Empire A at the beginning of the game, is attacked and seized during an enemy Combat Phase by Empire B. Later, during the same Combat Phase, the planet is liberated by a friendly Empire A fleet that (accidentally) retreats onto the planet and drives away the enemy forces. Assuming the planet ceases to be a supply point for the Empire A when the Combat Phase during which Empire B seized the planet is complete, when does the planet again become a supply point for Empire A?

Answer: Empire A loses a planet to Empire B on Empire B's turn. During combat and retreat, Empire A arranges for a retreat onto the now-conquered planet and liberates it from Empire B. It is, from that point, no longer a supply point for Empire B. According to rule (413.2), once a planet is (re)captured it becomes part of the old (new) owner's supply grid at the beginning of the next Player Turn after it is recaptured. So, at the beginning of Empire A's next turn, the planet will be considered part of the Empire A supply grid.

Question: When can you pay for supply for ships in a partial grid? (Any time? At any point you check your supply? Only during Economics 1A? Never, because it's not specified?) How long does the purchased supply last? (Until the next check? Until the start of the next player turn? Until the start of your next turn? Until the same point in the next Player Turn? In my next Player Turn?

Answer: The supply for being in a partial supply grid is paid during the owning empire's step 1A of the sequence of play. This is good for the entire turn (both players). If the partial supply grid is created during the turn, then for combat you have two opportunities to be in supply for combat: one is in 1A, the other is in 5-3A. If you are now isolated in combat, then certain things like salvage goes to the newly formed partial grid. Rule (413.41) implies that Economic Points can be produced in a Partial Grid (note that this existed before the salvage rules); (430.12) says that "only those planets linked to a supply grid and provinces that have one or more of their hexes linked to a supply grid produce Economic Points"; (413.1) indicates that a supply grid must include one or both of the capital or Off-Map Area; (413.4) says that a partial grid contains neither the Capital nor the Off-Map Area.

Question: So, Partial Grids are both permitted and absolutely prohibited from producing EP. Which is correct?

Answer: Both, a partial supply grid is not a main supply grid and main a supply grid is not a partial supply grid. Each has their own definition and each is treated separately.

Question: On a related note, is the intent of (413.43) to prohibit expeditionary fleets (411.7) from drawing supplies from their main supply grid, through the allied supply grid(s), then through their partial supply grid?

Answer: That is one of the effects.

Question: Also relating to partial supply grids: It's been ruled that, while units stacked with a base/planet in a partial supply grid are in supply, they still have to pay for their replacement fighters. Does this also apply to the base/PDU on the planet (i.e., do they have to pay for their fighters)?

Answer: The cost for supply is stated for units. A PDU is a unit.

Question: Is a ship that is in supply at the start of its Operational Movement automatically considered to be in supply for Retrograde Movement? Rule (410.24) confuses the situation.

Answer: Rule (206.31) is clear that a ship must be in supply at the time it wants to retrograde to use Retrograde Movement. The supply check during Operational Movement is no longer relevant. Rule (410.24) refers to the Retrograde Phase and allows a unit that was out of supply during the Combat Phase but in supply during the Retrograde Phase to retrograde.